I ported Blame to fabric and ran it on AoF3 to see what issues have been going around. I found this popped up in the logs. Basically, one of Mo' Structure's structure has minecraft:mostructuresvillager/villager instead of minecraft:mostructures/villager/villager in their jigsaw blocks or something but I do not know which structure it is. I can experiment later to try and narrow it down.

Also below that is [21:13:48] [Worker-Main-23/WARN]: Empty or none existent pool: minecraft:village/desert/street which might be part of the same structure. I was in a desert at the time. If this is part of the same Mo Structure, then this pool name is also a typo as it should be minecraft:village/desert/streets so hopefully with these typos fixed, your structure will spawn more complete now!

Edit: more pool errors are in the logs. I'll list them here:
[21:16:08] [Worker-Main-14/WARN]: Empty or none existent pool: mostructures:villager/market
[21:16:00] [Worker-Main-8/WARN]: Empty or none existent pool: mostructures:abandoned/village/churches

I went and improved Blame to actually give more info on what piece has the typo in the jigsaw blocks and so far, I could only find the villager feature and market errors. The minecraft:village/desert/streets must had been another mod so ignore that lol.

Here's the extra info!

Semi-fixed in 1.0.0. It doesn't really do anything now, only thing that remains is it trying to load a block entity from air, but that doesn't really seem to be a world-breaking issue preventing me from releasing a new version.