File talk:Ocean monument odd generation.png

Explanation
I have seen stuff like this happen when the structure location algorithm changes, as it did for example in Bedrock 1.10. Chunks already generated in a world prior to 1.10, along with their structures, were unchanged. But new chunks generated in the same world after 1.10 used the new structure locations. So if a new structure is to be generated in a new chunk, but the structure overlaps a pre-existing chunk, it gets truncated by that pre-existing chunk. This happens with large structures such as monuments, which span more than one chunk. I've also seen it with villages, where buildings overlapping a pre-existing chunk border are cut off.

Notice that the central cutout in your picture is 16×16 columns, and there are other similar cutouts on either side. Where the monument is missing, those chunks were already there in your world before your Minecraft was updated, and then the new algorithm tried to generate a monument in a new chunk at the border, but couldn't generate the whole thing because the monument overlapped the pre-existing chunks. ~ Amatulic (talk) 16:51, 19 September 2020 (UTC)