Trying to load a backup for a section of a world and it caused it to bug out and mess up.
Not sure what caused it.

I'm running the 1.12.2 pack, but the pack author recommended I make a post here and ask.
Here is the git link to that question with screenshots and more information:

xJon/The-1.12.2-Pack#547 (comment)

Unfortunately, I don't know how to fix this bug. I think it happens when you add or remove mods and the block ID lists shift around, but I have been unable to reproduce it it so I can can't really tell. I'm leaving this issue open because it really needs to be fixed, but I don't expect to be able to fix it anytime soon.