https://mclo.gs/kvwO91Z

Seems the comodification happens when com.yungnickyoung.minecraft.yungsapi.world.jigsaw.JigsawManager.getPosOfJigsawBlockWithName(JigsawManager.java:147). The world did have a lot of very tall structures, I don't know if that has anything to do with it. This was on a modded instance, heavily modded in fact, so perhaps there's some compat issues as well.

Also i suppose to add, i was trying to pregenerate like 4 different dimensions at once. That could easily have something to do with it. The other dimensions were modded dimensions, but there was also an overworld generation task.