Minecraft Wiki:Issues

This page's purpose is to list all the bugs players have come across. They pertain to the unmodified, unhacked game. Most of the single-player bugs also apply to multi-player

Version history also contains bugs that aren't listed on this page.

Bugs and feature requests can now be logged at Get Satisfaction: Mojang.

Notch focused the Beta 1.6 update on bug fixes, and fixed around 100 bugs and introduced around 65 new bugs. By 1.6.5, most major bugs have been fixed.

General

 * Occasionally, the level.dat file is re-written, causing you to lose your held items, and generate a new spawn. This will in general corrupt both the level.dat and the level.dat_old file, and if you don’t have a backup and was using an automatically generated seed, the seed will be lost forever (this will cause strange terrain generation when you will explore new parts of the world).
 * Sometimes you can see through everything; this randomly happens on all games on all platforms. Toggling the fog distance will change everything back to normal (Default key is F).
 * ATI users with 6.x drivers will not be able to run the game at all.
 * If you take a screenshot with the Minecraft window in a portrait orientation, it will throw an error.
 * The renderer occasionally "conks out" leaving the user with the dirt background or a black screen. If the user has the dirt background and attempts to do anything, it will then give the user a black screen. If you tab out, or try to click or press keys, it will crash (1.6.X).
 * When an arrow shot by a skeleton lands on a block of ice and the ice is then destroyed by the player in Single Player it will crash the renderer and the player will be left with a "saving chunks" screen followed by a black screen. This will make your save unplayable.
 * Walking down a 45 degree angle (1 block high drops) will not trigger the sound for footsteps. When the player stops moving, all the missed footstep sounds will be triggered at the same time.
 * When tabbing out of the Minecraft window in fullscreen mode, (F11) Minecraft will either crash, turn black, or go weird in some other way.
 * When you "save and quit to title" in SSP, the "Saving Chunks" bar does not appear.
 * For all items which use damage values to determine their textures (eg. logs, wool) the particles displayed when destroying will be that of the base item.

Terrain Generation

 * Sometimes, the game may reset the seed that the map generates from. This is a result of tweaks of the seed and terrain generation code that are regular parts of the game's updates.
 * The "same chunk rotation bug" that has been solved in version 1.3 still exists for all caves in generated worlds. The solution to it should be similar to the terrain bug. Here is a screenshot from a world generated with version 1.3 with some of the most prominent chunk marked. (Here is the bug report on getsatisfaction.)
 * Large sections of "floating blocks" have been generated on new worlds for some clients. Here is a screenshot from a world in 1.5_01. The error only seems to appear in coastal areas in a large scale, floating blocks include: dirt, leaves and logs so far with select ores. Snow blocks seem also to appear on water.(Modifications within the screenshot have not shown bugs before and therefore I did not believe that they contributed to this bug.)
 * Trees or Snow layers may generate above water/lava lakes, resulting in floating trees or snow layers. If you walk on one of those snow layers you will fall through it.
 * Water and Lava lakes can appear inside oceans, replacing the blocks.
 * Ore veins are moved 8 blocks north, 8 blocks east. It's unknown what is the reason to this move.
 * Sometimes the surface dirt layer will not generate properly, so instead you see bare rock.
 * If you save and quit a game while holding a steel sword then create a new world your character will have the sword in his hand and perform the putting away animation despite the sword not being an item in the inventory. This bug bug applies on other items too. (Map confirmed)
 * As of 1.6, Seeds that previously generated clay appear to no longer do so.

3D

 * 3D Minecraft has issues rendering chunks other than the one you spawned on and the ones directly around it.
 * Obsidian is too dark for the 3d at times.
 * Turning the 3D anaglyph on and then off may result in the surrounding terrain to change biomes.

Achievements and Statistics

 * The achievements "Time to Farm!" and "Time to Strike!" requires a wooden hoe and sword (respectively), despite the description not specifying and the player being able to build stone or better versions of these tools.
 * Throwing leather on the ground earns the achievement for killing a cow.
 * If creepers blow up a tree and you collect the wood, or someone tosses you on SMP a block of wood, you'll still get the "Getting Wood" achievement.
 * Achievements (& stats?) saved when playing offline and achievements saved when logged into Minecraft.net are separate and do not sync.
 * Deaths are not recorded in the statistics when the player dies in SMP.
 * Player kills are not recorded in SMP.
 * Bucket usage is not recorded in the statistics.
 * In the statistics screen the compass will point toward the equivalent of the spawn in the nether.
 * Shift-clicking to receive items from crafting doesn't count towards items crafted in your statistics.

Beds

 * Depending on the placement of a bed monsters will spawn on or near the bed regardless of light level. Sometimes this can occur even if the bed isn't touching any walls. Double doors also cause this to happen, the game thinks the room is "outside" allowing monsters to spawn inside the shelter.

Doors

 * If you close a door on yourself and jump, you can stand on the lower half of the door. This can be used to climb on top of doors.
 * If you stand in an open door and close it, you are standing inside the door and can exit either way. It does not push you away.

Furnaces

 * On destruction, furnaces may not drop a single item from the burn area.
 * The furnace animations may not work at times.
 * When being used, the furnace will glow brighter than a furnace not being used.

GUI

 * You are unable to directly swap items in your inventory if the two items are same. This is important if you would like to swap the same item type with two different durability values. This is a result of the way combining stacks works.
 * If a player enters a world, toggles debug mode (F3), then exits the world with debug mode still on, debug mode will still show.
 * If the player rides a vehicle and then opens their inventory, the player's hands will shift position in their view. This is most noticeable when the player has a map as their active item, and persists until the player opens their inventory again, even surviving save & quits.
 * Blocks held by the player will show as mirrored in the inventory. This is most visible with TNT (mirrored letters). The reason for this is that the items are rendered as one pixel-block thick, and rendered to be seen from the player's first person perspective. That means they look mirrored when seen from the inventory screen. (I suspect this would be the same for other players seeing the player in SMP too.)

Ladders

 * Placing ladders on snow layers make the ladder invisible but they still act as if you placed them normally.
 * If you place a bucket of water in a place occupied by a ladder with no other blocks next to it, the water will replace the ladder and you will not get the ladder back.

Lava

 * Sometimes, lava won't cause damage. More common in SMP.
 * If player stands above lava on a recently placed block when the game is on a fair lag, the block will be falsely removed by lag and the player falls into the lava and shows a fake burning animation.
 * If the Player stands in an Edge pointing to South-West and on the other side there is lava, then the Player will start to burn and recieve damage.

Lighting

 * Occasionally, some chunks of the map do not update with the day/night cycle, as seen here. Also, even in caves or closed environments the player can still see lighting bugs, (i.e. An area has full light and it has a small spot of full darkness next to it. When the spot is edited, it changes to normal.) These glitches are fairly common and can cause multiple problems. Usually waiting for a moment will fix this or you can simply toggle the fog.
 * Some mobs - pigs and sheep confirmed - will alternate between looking slightly darker, and normal "brightness", as they bob up and down while floating in water.

Mobs

 * Creepers may spawn in open areas with torchlight.
 * Squid can spawn in unintended locations, such as from cavern springs. This is more common in multiplayer.
 * Tamed Wolves will attack you if you shoot yourself with an arrow. This can be achieved by looking straight up, shooting an arrow, and moving forward a small bit to compensate for a small amount of curve. Another way is to shoot an arrow at the ceiling and stand directly under it and destroy the block the arrow is on. This will cause the arrow to drop and hit you.
 * Sometimes a tamed wolf may get stuck in the wall, causing it to slowly die. You can save him by breaking the block he is stuck in.
 * If you are riding a pig, and it walks into a low room that is not low enough for your head to be in the ceiling, you may start suffocating.
 * Wolves are known to stand up from their seated position randomly, and teleport to the player even though he is a large distance away. You may have to travel back all the way in order to put the wolf back in its place.
 * Squids do not despawn as of Beta 1.5, but slimes seem to despawn now.
 * When a creeper spawns in tall grass, Minecraft may crash.

Paintings

 * A painting placed over a light source does not block the light.
 * Paintings do not use the smooth lighting, even if all blocks around it do.

Portals

 * Going through a portal will cause a memory leak. Making this multiple times will reduce the available heap and forces more full garbage collections (known as lag spikes). If Minecraft runs out of memory it will crash.
 * After entering a portal the distortion animation can appear even if the player hasn't moved but this will not teleport the player back.
 * Trying to blow up the portal material with TNT causes the game to crash

Redstone Repeaters

 * A repeater will freeze upon save and reload of a world.
 * Repeaters won't power doors directly or through adjacent blocks.

Score

 * When the player dies, their score is displayed as "&e0".

Stairs

 * When climbing stairs, the camera shakes a lot more than when descending stairs.

Tall Grass

 * Tall grass blocks hang visually 1/16 of a block to the east.
 * Tall grass and dead shrubs don't appear on old worlds

Weather

 * Thunder sounds play even at bedrock.
 * Clouds pass through solid blocks and can enter sealed off areas.
 * Rain can't be seen through glass.
 * The snowflakes in 1.6.4 appear as small falling blocks not flakes of snow.

General

 * Advanced OpenGL will often clip visible areas, especially if you rapidly turn your mouse. Due to this issue, among others, Advanced OpenGL had been disabled between Beta 1.6.0 and Beta 1.6.5
 * Sometimes blocks will fail to render, creating massive holes on the ground and walls, allowing the player to see caves and dungeons under the map.
 * Sneaking prevents movement from Soul Sand or Cacti to any other block, however, you can fall off the block onto a lower half-step or stair.
 * On Linux, Minecraft is losing its mouse focus on every click to X Window for a very short time. If a pressed key is released at this moment Minecraft won't register this. This will cause you to move even if the movement key isn't pressed anymore. This is due to a bug in LWJGL that was fixed in LWJGL 2.6. Replace Minecraft's copy with a newer version of LWJGL to fix this issue. GetSatisfaction thread
 * Sometimes mobs within a certain area will stop moving, and entering the area will cause the player to become rooted to the spot and often vibrate wildly. Many animations, such as digging and health recovery will be broken, and mobs that the player hits will constantly loop the damage animation without dying. It is not possible to catch fire. This is often called a 'bad chunk'. Even if the chunk is deleted and generated again the bug will persist.
 * The audio position of the player lags behind where the player actually is. The supplied OpenAL DLLs lack 3D audio so it's hard to notice. However if you replace these DLLs with alternatives (such as the ones provided by the Creative drivers) you can notice that when you walk the footstep sounds are generated from where you were coming from, rather than directly underneath you. It is disputed whether this is a bug because it is not noticed with the provided DLLs, and 3D audio is something the game was not intended to support.
 * Selection bounding box breaks ATI cards' anti-aliasing. (Certain ATI cards don't support anti-aliased lines.)
 * There's a file called map.txt in the achievement folder inside minecraft.jar that causes performance issues. Removing it may greatly increase your performance, but may reset your achievements.
 * Unable to take a screenshot in full screen mode on some computers.FullScreen.jpg
 * Pressing a jump, movement, or sneak key then entering into your inventory will cause the action to be held. The inventory may then be closed, and the action will continue until the according key is pressed or the inventory is opened. Multiple keys may be "toggled" in this way, although the effect must be simultaneous.
 * When using custom biome tinting on leaves, sometimes there are parts of terrain where the leaves are darker than they should be. Trees can even be only partly covered by black leaves.

Audio

 * The openAL32.dll and openAL64.dll that come with Minecraft do not work properly. This sometimes causes Minecraft to crash when players turn sound on in the options menu. On Windows machines, deleting Minecraft's openAL files usually solves the problem, because Minecraft will then automatically use Windows operating system's copy of the OpenAL DLL, which works properly.

Arrows

 * Arrows that have not hit a mob become unobtainable if you die or save and quit then begin playing before retrieving them.
 * Tilling dirt with an arrow on it will cause the arrow to fall through into the next block.
 * Arrows that a player shoots rapidly occasionally hit said player. More common in SMP, most likely due to lag.
 * Arrows can be shot onto pressure plates then right-clicked on to activate the pressure plate.

Beds

 * You can break blocks while laying on a bed.
 * While sleeping, particles (torches, furnaces, etc.) do not "adjust" to face you, some of them may look flat or even be invisible.
 * Beds placed in fully enclosed areas (on both sides and with only one space above), or beds placed with no ground even with the block under the bed on either side (with only one space above), can cause you to wake up inside a wall, killing you and potentially destroying your items. This is due to player placement when you wake: if the game cannot place you on the ground level with the block below the bed on either the left or right side, it will place you on top of the bed. If there's only 1 block height above the bed, your head will become stuck in the ceiling, killing you.
 * Beds cannot be placed on snow.
 * If the player right-clicks the bed fast enough, they will recieve a message saying This bed is occupied even though they are on SSP. This is caused by the last click to attempt to get in bed being performed during the game placing the player in bed, tricking the game into thinking someone is already there.
 * Beds being broken appear to get brighter.
 * You can sleep while in a minecart or a boat. You still move with the minecart or boat but you may lose air when sleeping in a boat.
 * You can sleep during a thunderstorm, even during the day.
 * If you walk very far away from your bed and then die, you do not re-spawn at your bed and instead spawn at your original spawn point, receiving the message "Your home bed was missing or obstructed". This is probably due to the fact that the chunk has been unloaded.
 * Walking on a bed produces the same sound as walking on the block under the bed.

Boats

 * If you manage to stand on your boat while it is under water, the boat will be unable to rise. The boat will still retain horizontal movement, though, and will often slide out from underneath you.
 * If you save and reload while in a boat, you will no longer be in the boat.
 * Pressing F5 whilst in a boat will show your leg/foot armor protruding from the bottom of the boat, even though your character is sitting.
 * Standing on a boat causes jittering of the player, similar to the old fence bug.


 * Exiting a boat will sometimes cause the player to fall through it. This could be fixed by implementing code that would place the player one block higher than the boat when it's exited.
 * If an occupied boat crashes into an unoccupied one, only the occupied one breaks.
 * Attacking a mob in the water with a sword or bow that is close to you makes the game think that you're hitting the boat, and therefore damaging or destroying it.
 * Parking a Boat on a half step port while riding causes damage to player. Sometimes full health is depleted to zero.

Cactus

 * Cacti have a South/West rule for applying damage. Placing a block above a single cactus piece prevents you from stepping on the cactus and prevents you from taking damage by pushing against the south or west sides of the cactus. The north and east sides of the cactus can still hurt you.

Chest

 * A chest can still be opened when a transparent block (glass, slab, leaf) is placed on top of it.
 * If you are killed while having the chest GUI open and you transfer items from the chest to your inventory after you are killed, those items will be lost.
 * Dropping Items or blocks on a chest may disintegrate them.

Crafting Table

 * Dropping a block on top of the crafting table may destroy it, like cactus. This can be ignored by placing glass on top of the table.
 * Unlike other wooden blocks, axes aren't the most efficient tool to use to destroy crafting tables.

Doors

 * When doors are placed, they are oriented such that they swing open out and to the left from the player. As such, if the right door of a planned double door is placed before the left one, both doors will swing the same direction.
 * Double doors may fail to protect a sleeping player, especially if there are already hostile mobs outside the house. This is presumably caused by the right door somehow being ignored by the game when searching for a way for a hostile mob to come in. This is supported by the fact that only skeletons and zombies attack the player, but never spiders, because they need a 2x2 space to get in.

Farmland

 * Saplings can be planted on tilled soil, however they may not grow even when bone meal is used.

Fire

 * A forest fire can cause strange patches of light to be left after all the fire has burnt out. This can be fixed by placing a new block on the center of the lit area.
 * When the player is on fire, and is viewed via the inventory window or f5, the fire sprite originates at their head. This results in fire hovering above the player.

Furnaces

 * Furnaces emit light even if its face side is blocked. This is because the block itself emits the light, and it could be fixed by making the block in front of it emit light instead, but only if the block in front is transparent.
 * When you put coal and a smelting item in a furnace, then leave and re-enter the world, the fire icon glitches and will not shrink until the fuel source is about to run out.
 * The fire animation may not disappear even after the fuel is consumed.
 * After an use of a furnace, if there is unused fuel material inside the furnace, it will be invisible and burning animation is still played.
 * If a bucket of Lava is placed in a furnace, you do not get the bucket back.

Glass

 * While riding in a Minecart, one can pass through a block of glass above the rail block. (These first two properties for glass also hold true for single slab blocks. These properties are suspected to be related to the blocks' transparency.)
 * You can't suffocate while stuck in glass.
 * If you attempt to light glass on fire, the durability of your flint and steel is lowered without any flames appearing.
 * If a glass wall is placed next to TNT in water and you stand on the other side of the glass, you will always take only a half heart of damage.
 * Glass does not affect the orientation of chests and furnaces.
 * Snow cannot form on glass.

Glowstone

 * When glowstone is placed at the upper limit of the map, (Layer 127), the side surfaces of the block exhibit the usual luminance but the top surface exhibits illuminance which is dependent upon the environmental lighting level,(i.e time of day or night). It is suspected that glowstone behaves like this anywhere it is against the edge of the "blockspace" or space where blocks are placeable, like the edges of a map beyond where any avatar has ventured and at layer 1, against the void.
 * Redstone dust, ladders, rails, buttons, levers, and pressure plates cannot be placed on glowstone.

Grass

 * It appears that in arctic biomes, next to ice, grass can be generated underwater by the terrain generator.

Gravel and Sand

 * Gravel or sand will not fall down if it is placed above a non-solid block, like a torch or flower. If blocks of gravel or sand fall onto a non-solid block, they will accumulate into resources.Video
 * If you allow sand or gravel to fall on you, after moving around it is possible to be in such a position that you will not suffocate and you will be able to see through the sand or gravel and any blocks connected to the sand or gravel. This can reveal caverns and empty spaces.
 * If you place a sand or gravel block then quit the game before it starts falling, upon reload, it will float. If a nearby block updates, it will fall.
 * When a cave (or any opening) is generated in sand or gravel, the blocks will float until a space by it is modified in any way.
 * When destroying sand or gravel in SMP, the blocks will sometimes repeatedly fall down and teleport back to where it started. This most commonly happens when destroying a tall pile of gravel or sand with a shovel.

GUI

 * If you go from windowed mode to fullscreen mode, and then go back, the GUI's alignment is not correct, meaning your mouse will go to the leftmost part of the screen, no matter where the Y position of your mouse is.
 * If you disconnect from a server while a message is displayed, and then load a single player world, the text will appear in SSP as shown here.
 * In the debug menu (F3) the FPS counter may show Chunk Updates instead of FPS, usually while generating new chunks.
 * The debug menu may not be displayed properly when the GUI size is set to Auto.
 * Holding down or spamming right mouse button while holding down left mouse button will cause the "item action animation" to pause/stutter. The user is still able to mine, cut, etc while the animation has paused.
 * When clicking the Back to game button, the click may "pass through" into the game, causing the player to unintentionally execute the left mouse button action.
 * When in third person mode, if the camera appears to be above the water but the player's head is in the water, the GUI will still be darkened.

Ice

 * Ice blocks do not have the slide effect on their border if no other ice block connects on them.
 * You can see chunk borders in ice.
 * Pre-Biome chunks will generate ice, no matter what type the world was.

Ladder

 * Spiders can not climb a wall if a ladder is placed on it. (They get stuck in the small edge of the ladder)
 * When it is raining, and if you are going down a ladder, the rain will stop moving, when obviously the rain is faster than your speed while descending from the ladder. It is unknown if this is a bug or not, although it doesn't look like it fits correctly.
 * Under certain conditions, if you are looking at a ladder, the selected block will toggle back and forth between the ladder and an adjacent block.

Lava

 * Lava can sometimes fail to generate proper lighting into the surrounding area, and will not damage the player. These pools can be traversed one layer without injury - submerging into the lava will cause the player to take damage, as well as force relighting of the pit.

Lighting

 * There is a lighting bug in which levels below 32 are lit, causing immense lag when loading chunks. This effects the Sky Lands map and the Far Lands. (Research on the bug The cause of the bug another topic confirming the lighting bug)
 * Smooth Lighting doesn't work when shadows are cast on water. Example
 * Smooth Lighting acts weird on certain blocks like signs, doors, and other special blocks.
 * On some systems, nighttime can appear excessively dark (issue dates to approximately Oct-Nov 2010). GetSatisfaction thread
 * Blocks placed above snow-covered grass cause the lower blocks to appear darker than they should, but only with smooth lighting. Get Satisfaction thread
 * There exists an underwater lightning problem which is most likely located at chunk borders. Example
 * The top face of a button will appear darker when smooth lighting is on. This does not matter on what other lighting or blocks is near it.

Maps

 * Destroying a map does not remove that number from the map list. If you made one map, then fell into lava and it burned, the next map you make will still be called Map 1, instead of becoming Map 0.
 * Sometimes while viewing a map the game will switch to a "saving chunks screen" then end on a black screen.
 * At times, the player's marker will spontaneously disappear.
 * Crafting a map underground and using it sometimes makes Minecraft crash.

Minecarts

 * If a minecart is partially off of a sloped Powered Rail, in such a way that it does not move, and the player enters and leaves the cart, they may fall through the block beneath it.
 * When minecarts are placed on a small circular track, they will gain momentum from colliding with each other.
 * Riding a minecart at the top of the map makes the player invisible until you leave the cart or ride downwards.
 * Sometimes minecarts disappear completely for unknown reasons.
 * Minecarts can go off tracks or crash through the ground if their momentum is too high.
 * When exiting a minecart, if there is only a single block free above the track, the player will take damage from suffocation.
 * If you start sneaking right after destroying a minecart, you may crash and get buried, but there is also a chance you will get multiple minecart drops.
 * When exiting Minecarts when there is a block in front, the user may rarely fall into the block beneath the cart.
 * If TNT is detonated near a minecart, it occasionally drops more than 1 minecart.
 * A player/mob can be in a burning minecart without taking damage or being set on fire themselves.
 * Water does not put out burning minecarts.
 * When interacting with a Minecart+Chest or Minecart+Furnace while holding a useable item (e.g. filled bucket, bow and arrow, food), the item will be used when the chest is opened (bucket emptied, bow fired, food eaten).
 * Flowing water no longer affects minecarts as of a recent version.
 * Minecarts will interact with blocks next to the track while turning. When a track turns to North or South and there is a block next to the turn track, a minecart will stop rather than make the turn. This does not seem to happen on turns going to East or West.
 * When a minecart goes around a U-turn at extreme speeds, the player's viewing angle may not spin around, and will rather stay facing forward.
 * If the player saves in a minecart, they will be ejected from it and multiple copies of it will appear, possibly getting stuck right next to each other so that they accelerate at high speeds. If this happens to minecarts with chests, the items inside the chests will be duplicated as well.
 * Powered Minecarts no longer push other minecarts if moving east-west.

Mobs

 * If a mob is riding a minecart and 2 or more mine carts get stuck in each other, after destroying or moving the carts away from the other carts the mobs will be invisible.
 * When up close to a Zombie Pigman, the inventory GUI will become much brighter.
 * Ghasts will shoot at the camera, not the player entity. This frequently causes fireballs to miss you in 1st person. The deviation is even larger in 3rd person view.
 * Squid still can't swim up in Beta 1.5_01; or perhaps they can't swim up again (according to Squid this was fixed in Beta 1.3).
 * Mobs can move briefly before map data is loaded when signing out and loading the world, usually resulting in the mobs getting stuck.
 * If a wolf is tamed when it's attacking another mob, it may still attack it when on sitting animation.
 * If a Tamed Wolf is left sitting when you exit the game and you return to the game in offline mode, the wolf will not respond to the command to stand up and follow.
 * If you hit a pig with a saddle (by left-clicking) it will deal normal damage but it will also place the saddle on the pig. This can cause you to lose the saddle as you may accidentally kill the pig, especially if you have wolves around.
 * If a creeper attempts to reach the character by running into a corner, and the block it is on is a ledge with no blocks on its level (or possibly above it), the creeper may stop as though it is hiding, then never move from that spot again unless the player breaks a block or moves the creeper to change these conditions. If the character moves to the other side, the creeper will randomly snap between staring at the player without moving and looking around as though it doesn't see the player. If the player gets close enough it will still explode.
 * If a block is placed directly above the water, and a wolf swims against it, it gets stuck and suffocates unless the block is removed.
 * After getting out of water, wolves may shake themselves while jumping, or if told to sit, wolves will shake themselves in a sitting position.
 * Tamed wolves or any other mob, whether friendly, neutral or hostile, will not avoid harmful blocks, such as cacti, fire, or lava.
 * If a player descends from a cliff, a tamed wolf will jump off the cliff to get to the player, regardless of the cliff's height, rather than waiting to be teleported.

Nether

 * The lighting in the Nether can flicker in the distance as if in a thunderstorm if there is one raging in the over-world.

Paintings

 * Paintings can be placed inside snow.
 * If a painting is placed on a block with a fence on top, the painting may be 1x2 in size. This can not be removed without breaking the block or fence.
 * A broken painting will rarely drop 2 paintings.

Portals

 * Being killed in the Nether will cause chunks and a portal to be generated near your relative location on Earth, as though you had teleported back from the location at which you died normally.
 * Dying while in the Nether will also ignore a changed spawn point (via sleeping).
 * If the game is closed while entering The Nether, you will be sent to your spawn point on earth without held items, as if you were killed. However, it ignores a when the player's spawnpoint is changed via sleeping.
 * Portals over 2 km away from each other in the overworld will link to the same portal in The Nether. To fix, you have to build another nether portal manually.
 * When returning from the nether in a portal it can sometimes spit you out in odd places miles from your original portal. example video(Originally spotted in Part 17, It switched again in part 18 (from the beach to a cave) then explored in part 19, finally dug to the surface, along with spotting the beach portal in part 20)

Pressure Plates

 * Pressure plates (both wood and stone) have an odd fade to black gradient when smooth lighting is on.

Rails

 * If a powered rail is placed directly adjacent to a slope and the power source is a lever hidden in a hole in the wall, riding over that rail will cause both the minecart and the player to be teleported into the hole in the wall, causing suffocation damage or death.
 * If a rail is powered by a button that is directly above the rail and there is redstone wire leading from the block right behind the button, pressing the button causes the rail to be powered untill the rail is destroyed or redstone is connected to the rail.
 * In 1.6, water destroys rails instead of returning it.
 * More bugs at Powered Rail Bugs.
 * More bugs at Detector Rail Bugs.

Redstone

 * The particle color while destroying a redstone wire is grey (since Beta 1.3, because of dynamic colouring).
 * If redstone dust is placed on top of the same block as a redstone torch, and a block is placed over the torch, they will connect in a strange way that makes them flicker.
 * I placed powered rail, and a lever 1 block too high. I then placed Redstone (wire) on the ground to supply power to the rail. When I broke the wire power was still supplied, however the connection was no more. Flipping the lever did nothing. I have not tested this on multilayer yet. And I might be wrong and Notch wanted this...IDK. (Post something here: http://www.minecraftforum.net/topic/347522-chat/) Tell me what you think about this glitch: (Purpose or Accident.

Redstone Repeaters

 * Cheated Redstone Repeaters (id 93 and 94) have the same texture as a double slab.
 * Redstone Repeaters don't always toggle correctly; when a circuit is switched on, some repeaters stay off and vice versa.
 * Can happen multiple times over the same circuit.
 * More likely to happen over longer distances.
 * Removing the Repeater and then replacing it will put it into the proper state, but the problem can come back at any time.

Sapling

 * If snow, fire, water, or lava are over a block, a sapling may be placed on that block even if it is not a dirt block. After a short time the sapling will recognize that it is illegally planted and uproot itself.
 * If flowing water hits a sapling, the item won't be dropped.
 * A tree can grow on top of a player, suffocating them.
 * If a sapling is placed next to another sapling under low lighting conditions, both saplings will be turned to item form.

Sign

 * When placing a sign upon a block which is eight blocks higher than the level upon which the avatar is standing, requiring the use of the space bar to "jump and place", the sign edit menu is activated whilst the player is in mid-jump. Upon exiting the sign edit menu, the player continues to jump until the space bar is used again.

Sugar Cane

 * If a block is covered in fire, water, or lava, sugar cane can be placed on that block violating the usual placement rules for sugar cane. When the sugar cane grows it will recognize that it is illegally planted and uproot itself leaving two loose sugar cane blocks.
 * Bugs in the terrain generation code can cause Sugar Cane to float. This is a purely visual bug. You can see the selection box when you look at it, and changing nearby terrain makes it show up.
 * Ghasts can not see you through sugar cane.

Snow

 * In snow biomes, water and lava lakes can generate below the snow and leave some of the snow floating. Players will fall through this floating snow.
 * Beds cannot be placed on snow.
 * Snowballs cannot be obtained when shoveling snow off of a sand block.

Slabs

 * When firing arrows at the opposite corner of the slab, your arrows may clip through and hit the block behind it.
 * Wooden slabs can currently only be properly collected with a pickaxe instead of an axe. This is caused by all 4 slabs using the same block id, with varying "damage" values.
 * When walking with 50-100% of your body over a slab, whilst being at the high of another block, the walking sound effect for the slab type will play, rather than the one which you are actually on.
 * A single slab cannot be made into a double slab if there is another solid block directly above the single slab.
 * Minecraft places the slab normally first, then realizes it's on top of another slab and combines them.
 * Torches, and other nonsolid items, can not be placed on single slabs.
 * It is impossible to be suffocated by single slabs.
 * With Smooth Lighting on, a slight amount of light can be seen passing through the sides of slabs. This does not affect mob spawning.
 * If a slab is placed on ice, it still has the "slippery" effect.
 * If half blocks are placed next to TNT, the damage is significantly reduced.
 * Neither single nor double slabs displace item entities.
 * When exiting and reentering the game while standing on a single slab with empty space below,you sometimes fall through the slab.
 * When putting a slab on a slab which has another slab below it (or more) all slabs combine into one double slabs block, thus losing one (or more) slab in the process. (see example : http://www.youtube.com/watch?v=LIyYUaI0JHs)

Tools

 * Axes do not break certain wooden blocks faster than hands, like you would expect. These blocks include wooden stairs, fences, wooden doors, signs, crafting tables and jukeboxes.



Water

 * Under certain circumstances, underwater and underlava players can breathe, and see through the water. An example is shown here(somewhat fixed in Beta 1.5_01, harder to replicate, but still possible to do)
 * Water sometimes doesn't flow into newly generated areas (usually when a cavern is being generated near a body of water).
 * Unlike Glass, other water blocks are invisible when viewed through a waterfall, even though there is air in between. Example.
 * Water source blocks do not regenerate over other water. Get Satisfaction: Water thats 2+ levels deep doesn't refill correctly.
 * Similarly, water that propagates from a source block above it does not generate source blocks below (used to be the case before 1.6). This makes man-made lakes very difficult to swim in, and can trap you in a downward current if you dig a hole on the ocean floor.
 * When opening your inventory when swimming, you can only move left or right until you move.
 * Upon entering a newly generated map, water may be found floating in midair.
 * When in third person and underwater, the view will be darkened even if the apparent camera position is above water. And vise versa (you being above water, camera being below)

Weather

 * The outside ambience sound for rain plays while under glass.
 * Wolves get wet while under glass during rain.
 * When lightning strikes, ice, water, portals, rain, snow, and other particles behind it become see through.
 * When rain puts out a fire on Advanced OpenGL the area will sometimes stay lit.
 * Rain sometimes falls in snow biomes, and it sometimes snows in biomes other than Tundra/Taiga.
 * Sometimes rain and snow both fall at the same time in the same biome.
 * Rain and snow fall above the cloud layer.
 * Rain does not pass through signs.
 * If you open your inventory when it is raining or snowing, the sun will be visible.
 * If you save during rain and load later, you won't hear the rain's ambience sound.

Mac OS X

 * On some Mac OS X Systems, the World Select screen will not appear at all, making the game unplayable on those Mac systems.
 * In other cases, the Mojang AB logo will appear green and the title screen and the game in dark areas will appear red.
 * Since version 1.3, on some Mac OS X systems, when the player closes the game (clicks the X button on the window) the computer will freeze up completely. The mouse will still move, but nothing else responds, forcing a hard shut down and restart. In addition, the system does not acknowledge the issue (eg, no crash report window, no system.log entries). When on an afflicted computer, this rarely may not happen (often after a reboot or game update).
 * Afflicted systems seem to be older 32-bit Intel Macbook models, such as those made in and around 2007.
 * GetSatisfaction ticket for this bug
 * A work-around is to save to the title screen, and then Force-Quit Minecraft, instead of properly closing it.
 * It appears to only affect users with Intel GMA 950 graphics processers, known for its incompatibilities with 3D games.
 * Minecraft does not respond to either the Quit item in the Minecraft menu or it's shortcut, ⌘Q. This can be fixed by closing the window, then quitting Minecraft.
 * Pausing the game and expanding the window (+) as soon as the map is loaded causes a kernel panic, forcing you to restart the computer.
 * The game runs slow on Mac OS X 10.6 using a NVidia GeForce 320M graphics chip, however it runs with 60 or more FPS (average 120) on Ubuntu, using the same system.
 * Minecraft uses an 8-bit depth buffer on many macs, including brand-new high-end ones. This makes distant objects look terrible! It can be remedied by specifying the size of the depth buffer when creating the PixelFormat for the OpenGL context. Changing Display.create to Display.create(new PixelFormat.withDepthBits(32)) in net.minecraft.client.Minecraft.startGame fixes the problem. Look at this before and after screenshot and notice the huge difference.
 * On some Mac's, there is no audio, when you turn on the sound on Minecraft, the game hangs for a minute, then returns to normal, but still no audio. Otherwise, try holding F3 then press S while you are in Minecraft.
 * Since a recent update (roughly on 5/1/2011) to MacBook Pro's (2011 model), there are patches of white in the sky on many users clients. Additionally, the health bars of items are white and the background to the inventory and options menus are completely white. Also, when you sleep it becomes all white as well. Force updating the client does nothing to help nor does updating your Java.
 * One user noted that after removing the Minecraft folder in /Users/nickname/Library/Application Support the problem is fixed until you change something in the gfx settings of Minecraft. After you change the settings the only way to fix it back is to remove the folder again (manually switching to the default settings doesn't fix it)
 * GetSatisfaction ticket for this bug
 * Another user noted that it can be fixed by turning off Advanced OpenGL and then restarting Minecraft. However, the problem returns when the user turns Advanced OpenGL back on. Since the game performs better with Advanced OpenGL on, users still consider this a bug.
 * For the update 10.6.4, where Notch removed the Advanced OpenGL option, the bugs corrected themselves, but when He added OpenGL back into the game with 10.6.5, the bugs returned.
 * On some Mac OS X systems the bar on saving chunks won't render.
 * When using the Spaces Mac OS X feature and setting Minecraft to a specific space and, while in-game, pausing it and moving to a different Space will cause hardcore performance issues on your computer until moving back to the Minecraft space and focusing Minecraft.

General

 * If a player has respawned, he can place blocks on the block he is currently standing on. This will not decrease the block count in his inventory, effectively cloning blocks. This bug only occurs with non-opped players.
 * Full server world saves do not reliably save the entire world. This can be proven on a single person private server with whitelisting enabled when attempting to do a full server save via:
 * 1) Disabling incremental level saving with 'save-off' on on Minecraft console.
 * 2) Forcing a full save to disk with 'save-all' on on Minecraft console.
 * 3) Archiving and saving the archived world with 'tar -xvzf save.tg world' on shell in secondary system console.
 * 4) Turning back on incremental level saving by doing a 'save-on' on Minecraft console.
 * Enormous, cuboid areas (usually one or two chunks) of unfinished map open in random places. Caves, minerals, water, magma and mobs are visible when a Player peers into one of these voids. These areas cannot be walked on, causing a "[user] moved wrongly!" message to appear in the Server; however, players can ride minecarts through them with relative ease. Players can, however, walk "into" one of these voids (if it appears in front of him/her) resulting in the player falling repeatedly until the map renders itself. If the void appears in the middle of water, Players can "float" over the void using a boat. Placing a torch next to one of these "void holes", dumping lava or water nearby, or disconnecting and reconnecting to the server will make the land inside of them reappear. These have become significantly less common since the 1.3 update.
 * When you sneak (in third person), your character's feet are "in" the ground.
 * Occasionally, the level.dat file is re-written, causing Minecraft to generate a new spawn. Also occurs in SSP.
 * Seemingly as of Beta 1.3, some players have been getting huge amounts of strange lag. They get good FPS, but everything from placing blocks to damaging mobs can take anywhere from 10 seconds to 6 minutes. It is apparently related to the server, and NOT client-side. The server recieves the data, but takes a long time to send it back out. It appears to only affect 1-2 people at a time, coming and going randomly.
 * As of Beta 1.5, this problem seems to be less severe, but still exists.


 * A minecart track destroyed by water from above will disappear.
 * Using the /tp command to teleport to a distant individual can result in a lack of level data, causing a constant falling and then jumping of the camera.
 * Ambience sounds do not play in SMP.
 * You can cause a glitch whilst talking to other players, by holding down 2 or more keys at the exact same time. This causes the keys to go faster than normal for holding down one key. (Spammers exploit this method.)
 * The world data and the inventory of a player are not saved synchronously. If a player puts an item in a chest and the server crashes, the item will be both in the chest and the inventory of the player (duplicated).
 * Some players have issues where they can send information to a server fine, but have large amounts of lag when receiving information from the server. This results in SMP being unplayable for players who experience this bug.
 * Sometimes the client is slightly off on the position of other players, causing them to consistently appear slightly off of their actual position. This can cause players to appear to be inside floors or walls.
 * When collecting a block/item on the ground, the icon in the inventory's hotbar does not distort for a short time.
 * Thrown snowballs, eggs and fishing rods have no effect on players, only on mobs.
 * Eating mushroom stew frequently doesn't return the bowl. The empty bowl is visible for a moment in your hand before vanishing.
 * Players and mobs standing on the highest possible point (y 128) of the map will be invisible.
 * Sometimes when connecting to an SMP server, an 'End of stream' message appears. After this message appears, the Minecraft client may need to be restarted or left alone for roughly 5 to 10 minutes before it will work.
 * When your health regenerates in SMP (on a Peaceful server), the health bar does not "flash".
 * Notably with Sand, the sand may continue to hover in the air after being mined out and continue to bob up and down. Placing a block in the spot does NOT override this.
 * Also, blocks mined on the edge may continue to show the dropped block animation falling repeatedly. Retrieving the block at the top of this cycle will allow one to pick up the block
 * Occasionally players will become invisible to each other at random times for no particular reason and will subsequently reappear just as randomly. Players may still interact with each other (damaging each other, mining terrain, etc) but will be invisible.
 * If you disconnect while you are falling, you will not take fall damage, after you reconnect. The same applies for any form of damage. This is due to the 3 second invincibility period after respawning/logging in.
 * The state of every animation of broken blocks seems so be sent to every client causing massive lag (for example some TNT explosions)
 * Shift-clicking an item from a container/inventory into a full inventory/container will cause the game to crash.

Arrows

 * Arrows shot onto a wall cause the arrow to create a flickering wobbling repeat of the arrows movement. This happens mainly on glass.
 * Fired arrows will appear to come out backwards at first, then continue on a regular trajectory.
 * Arrows often appear glitched and stay in mid air, going back and forth, even if they hit a mob or another player.
 * This is especially common if multiple arrows are being shot.
 * A heavy arrow deathmatch causes severe lag on the server, takes minutes to recover. (picking up the arrows helps)

Beds

 * Sometimes when a player is sleeping and other player walks on that sleeping player the sleeping player will fall through the bed and the floor.
 * Trying to get into bed while sneaking disconnects the player(Illegal Stance).
 * If someone uses their bed in SMP, other players may get disconnected(Unrecognizable Packet ID: 17).
 * Attempting to hoe under a bed that would experience the monster spawning error would kick the player that used the hoe (illegal stance).
 * When right-clicking on a bed constantly before it is nightfall, the server may register that the player enters the bed, while the client believes the player is still not in the bed, causing the error message, "This bed is occupied," even when it appears there is no player inside. Other players will see the affected player moving around while he is in a sleeping pose.
 * The above "this bed is occupied" glitch sometimes also seems to occur if a player tries to enter a bed mid-jump.
 * If you try sleeping in a bed on SMP server while standing on it, it will start giving message "This bed is occupied" and you will be allowed to freely walk, but you will be really sleeping. Players will see you move but you will be lying down. You cannot trigger pressure plates while "sleepwalking", nor pick up items.
 * If you place your bed in a cave and try to sleep in it at night, a mob will spawn right near you and will attack you
 * A right-hinged door (when looking from the outside) will act as though there is no door present and as a result, you will be attacked while trying to go to sleep.

Boats

 * If you ride a boat over a chunk of water which did not load properly ( ex. the water is really there, but you can't see it and can see through the whole world ), the boat disappears.
 * Standing on a boat causes jittering of the player, similar to the old fence bug.
 * When a Boat gets damaged (by a player), it does not shake.
 * If you see a player riding in a boat, it sometimes looks like they are running in the boat, rather than sitting.
 * If you exit a boat, you may get stuck standing on top of the boat, constantly falling and being reset by the server. This is similar to how fences used to act. You can get off the boat by getting out while it is moving, as the boat will slide out from under you and eventually allow you to fall into the water.
 * This may kick you from the server with message "flying not allowed"
 * The boat turns in intervals of about 10-20 degrees, making turning extremely difficult in tight spaces. In between intervals of turning, holding left or right will cause the boat to strafe left or right, respectively.

Compass
This was listed as fixed in Beta 1.6 but does not seem to have been Example in 1.6.4 (half way through the video)
 * When spawning or crafting a compass in SMP it does not take you to your spawn, it creates a totally different 'north' example (watch to the end for confirmation of original spawn)

Detector Rail

 * When placed immediately next to a track switch, will crash the server.
 * The detector rail uses a stone pressure plate in its recipe, yet behaves like a wooden pressure plate. There is no way to create one that behaves like a stone pressure plate.

Dispensers

 * When a dispenser dispenses an item, there is no smoke puff and no sound is heard.
 * Shift-clicking items will cause game to crash

Fence

 * When standing on a fence, a player may be kicked for flying.

Fire

 * Some safe fireplaces in wooden houses have (as of the 1.6 update) burned said houses down.

Furnaces

 * Furnaces can stop smelting items during a severe lag.
 * Furnaces occasionally turn to another direction after being placed. Appears to be random.

Jukeboxes

 * Setting a jukebox on fire when it is playing a disc may cause the game to crash.

Lighting

 * The lighting engine often takes an abnormally long time to update when a light source is placed, and occasionally will not update at all, leaving the area pitch black even in the presence of say, a torch. This started in 1.6.X.
 * In 1.6.4 SMP with fast graphics new surfaces exposed by breaking blocks display black until a nearby light source is changed (removed or added). See GetSatisfaction thread at Two bugs: light doesn't update, redstone circuits don't work properly

Lightning

 * Lightning can strike inside houses and caves (is this naturally?). If lightning strikes you inside a cave you will catch on fire (no rain to put you out).
 * If Lightning strikes a painting, it causes a server exception and crash the server. (Caused by net.minecraft.server.EntityPainting.damageEntity)

Maps

 * When the servers view distance is set to a lower number "in my case 5" walking with a map may cause the server to lockup, setting the view distance back to the default of 10 fixed this.
 * If a player moves too fast horizontally while holding a map (usually from flying or teleporting) Chunks will stop loading for that player, and possibly other players, eventually kicking them out of the server due to timing out, and will not be able to log back into the server until it's restarted, despite other people being able to connect fine.
 * On some servers, going /home while holding a map will crash the server.
 * On some servers, a line of void may appear on the map. The server will disconnect you returning an error 500 if you approach of this area while holding a map.
 * The direction cursor appears to be off by about 22 degrees clockwise. This is likely the result of rounding error as the game rounds the players angle to within 1/8th of a rotation. [ie Rotation = floor(Angle / 8) * 22.5]

Minecarts

 * Engines consume coal but do not move under their own power, making them useless.
 * Empty/Storage Minecarts start to behave strangely when they are too far away from the Player. They disappear completely, disappear until Players disconnect and reconnect, or suddenly stop on tracks despite having sufficient momentum.
 * Minecarts load before terrain sometimes causing them to be invisible until they are interacted with. Large transit systems and door water boosters are examples of when the issue occurs. (log out/in to reproduce).
 * Minecarts being destroyed do not wobble.
 * When you're trying to send a Powered Minecart to a destination that is far away, the minecart stops after a while and never reaches its destination. But if you approach the powered minecart, you can see it moving again : you have to stay close to it.
 * An unpowered Powered Rail does not stop or even appear to slow down a Minecart when it is travelling very fast.
 * Three unpowered pieces in a row seems to stop it every time but frequently on the last piece.
 * If a mob spawns on a powered track circuit it will be pushed around it. Example
 * Stacked Minecarts glitch out and jump up and down.
 * An empty minecart too far from a player on powered rail will come back, when it would stop at the end had a player been with it.

Mobs, Hostile

 * Shooting animations (Ghast fireballs/opening mouth and eyes, Skeleton arrows) are not always visible. The sound of these actions (Ghast scream and Skeleton "twang") cannot be heard either.
 * Ghasts' fireballs occasionally do not explode, only lighting a small area on fire.
 * Sometimes mobs freeze in animation and can not be hit. They disappear after about 2 minutes. They are client-sided, so no other players will see them.
 * Some users are reporting mobs will be invisible, but can still attack you. On update 11/24/2010 SMP health update post Notch explained that to see invisible mobs, players must set their difficulty to the server side difficulty or higher.
 * This does not always fix the problem; on occasion, mobs will fail to load client-side.
 * Sometimes when the character dies, monsters will stay loaded client-side and not be loaded on the server side.
 * Sometimes players can hit mobs multiple times before the server registers the hit. The hits will then all register at once and the mob will be subjected to several knockbacks at once, flying into the air.
 * When a mob dies, its corpse sometimes sticks in the red death animation and doesn't despawn.
 * When slimes divide in SMP they may create client-side duplicates.
 * The lower half of mobs can not be hit with a melee weapon when you are 1-2 blocks below them. They can, however, be hit from directly underneath.
 * If escaping a Creeper and they do not explode, they will stay puffed up and explode imediantly after you get close enough, even after giving them the cool down time. While expanded, they act as though they are the size they look, allowing them to jump 2 block heights.

Mobs

 * Sometimes, Mobs of all types sink of 1 blocks in the ground, resulting in almost invisible mobs and darker mobs.
 * Sometimes mobs take no damage falling into running water less than one block deep, even if the player takes over 10 damage falling the same distance into the same water.

Mobs, Passive

 * Squids can fly upwards.
 * When a pig is struck by lightning, you get client-side pig zombies that cannot be killed (in addition to the server-side one)
 * Copious amounts of tamed wolves in a concentrated area prevent the spawning of nearby passive mods (easily up to 10-chunk radius).
 * Occassionally after dying a sheep they will still yield wool in their original color (i.e. white).

Mobs, Friendly

 * Occasionally, Wolves can disappear on SMP Servers, Disconnecting and Reconnecting fixes this.
 * Sometimes after reconnecting to a server, wolves that were previously sitting will appear to be standing. They will still behave as though they are sitting.
 * Occassionally when wandering a significant distance from a sitting wolf, it to teleport to your location and become active.
 * Sometimes after you go to sleep or are away for a while, your wolves will appear standing, although they act as they are sitting. This happens in both SMP and SSP.

Note Block

 * Note blocks and especially note-block-combos tend to react really easily on server's lag. Unable to make any longer noises / songs with note blocks on multiplayer.

Paintings

 * When copying an SSP world onto an SMP server, paintings are removed in the transition.
 * Paintings can be destroyed in spawn-protected areas.

Portal

 * As of 1.6.X, there is a chance of Minecraft's renderer to stop functioning (you can hear the audio going normally, and the server still registers you as playing), leaving you with a black screen, when you use a portal in SMP. Rejoining the server fixes this, but is a workaround.

Redstone

 * Since Beta 1.4, pulsars do not work, and many circuits have become glitchy in SMP.
 * Sometimes after waiting long enough (10-20 minutes?) a pulsar will start to work.
 * The particle colors for Delay/repeater blocks are the same of pumpkins.
 * The display of redstone differs from it's behavior when placing a block with torch on top next to a redstone wire (as well as on redstonewire-edges).
 * Giving redstone torches short pulses (via edge detection) causes them burn out, even if there is a pause > 5s between pulses
 * As well as repeaters, torches lock their state randomly when being wired for clock generating
 * While destroying a block, quickly applying redstone repeatedly will cause you to see textures of different blocks.
 * Redstone Repeaters occassionally become locked if their chunk becomes inactive while they are in their "on" state.
 * Occassionally Redstone does not properly turn on/off when you remove/add the block powering it (http://getsatisfaction.com/mojang/topics/smp_repeater_bug?topic_tools=open)
 * Redstone torches will sometimes disappear if attached to the side of a block that is in a different chunk (to the east or west) than the torch. They may also disappear under other conditions. (http://getsatisfaction.com/mojang/topics/redstone_torches_disappear_in_smp)

Signs

 * When a sign is placed in multiplayer and text is entered (but not finalized), and a torch is placed within 10 blocks of the player who placed the sign (not the sign, but the player), the entered text disappears. Interestingly, when a torch is placed within 10 blocks of the sign placing player BEFORE the sign is placed, any subsequent text entered will not be erased by torches placed OUTSIDE the radius of the first torch, but text will be erased by torches placed INSIDE the radius of the first torch. Oddly, this behavior only seems to occur with torches, though these tests were not exhaustive of the minecraft block set, and further work should be done to verify this claim.


 * Similar to the above effect, "active" sign text is reset if a cobblestone block behind and to the left of a sign is mined out and regenerated by a cobblestone generator

Time
using a bed to change time does not affect the clock generators. Restarting server fixes it quickly.
 * The server command /time breaks 'clock based' circuits

TNT

 * A TNT block meant to drop will enter a repeating fall animation (but not actually fall) when lit.
 * A TNT block can also explode twice, but this will not damage the environment twice.
 * If a lot of TNT is lit, some TNT may explode but leave behind an image of an exploding TNT block that is almost completely white, and will hover in mid-air while repeating the falling animation. The ghost TNT will not disappear unless the player disconnects and reconnects. (This is a client-side TNT entity)
 * Too much TNT detonating at once will freeze the client, often requiring the game to be closed. Though the client freezes, the server has just a short peak of CPU usage, which results in no noticeable lag in other areas most likely due to particle invisibility and/or the nonactive chunks.
 * The explosion result differs between client for ~5 seconds, as soon as the chunks update, the serverside calculated explosion will be shown.

Trees

 * Trees that have grown recently, especially packed together in a tree farm, sometimes don't update the client with the leaf positions. This creates "invisible" leaves that the player can't walk through and makes navigating tree farms an annoyance.
 * Using bone meal to quick-grow trees will sometimes cause "floating" trees to grow with the sapling still at the base. Removing the sapling or using more bone meal can cause the tree to grow into an enormous bundle of leaves with no log base. These leaves will now respawn immediately after being harvested. The only way to remove these glitched leaf blocks is to burn each block individually (fire will not spread for some reason) OR set the floor below the leaves on fire OR build an umbrella above it, the shadow seems to instantly vanquish the leaves. - This glitch is vastly more common when quick-growing trees under another trees foliage. Again, disconnecting and reconnecting will reset these "ghost trees."
 * Planting a sapling and waiting a bit will sometimes yield tree trunks with weird distributions of leaves, and in some cases, no leaves at all. Trees can also grow but be invisible, making it impossible to traverse a tree farm after a while. Rejoining the server appears to make invisible trees visible again and fire will swiftly cause phantom foliage to be made manifest. You can also place a torch to make the phantom foliage appear.
 * Leaves from trees will overwrite some blocks, such as a nearby fence. This is problematic when it renders areas previously thought safe accessible to hostile mobs.
 * Placing a torch on Leaves does not make the 'pop' sound for the item being placed.
 * Birch saplings will not grow in underground tree farms, even though there is proper lighting.

Tools

 * The last use of any tool causes a block to not drop, unless you normally get a drop from using your hands.

Water

 * You may find yourself drowning despite having a full breath meter. This is caused by the client registering that the player has gotten air, but the server registers that the player is still underwater. This causes the non-synced breath meter.
 * In some underwater areas there are lines of lighter spots at the bottom the water, likely on the edge of chunks where the next chunk over used to be empty space (causing light from the side to reach the bottom on the edge of the chunk)
 * Sometimes you can reset your breath meter by going against a block. However, you occasionally start drowning before the meter runs out if you do this.
 * If you press F5 (go to 3rd person) and are in deep water, you can see clearly underwater by moving your camera under the water while you're still swimming.

Web

 * Sometimes when slowly falling thourgh web, the web changes to stone (which is seen only clientside) and gets repeated damage till moving out after what it's seen as web again.