https://paste.dimdev.org/uyosukohax.mccrash

This pretty much cripples any attempt at starting up a world. I don't know if you're still supporting 1.12, but I'd advise at least fixing this.

@CursedFlames

Uh yeah, I'll fix this whenever I can get my 1.12 dev env working again

This is caused by a typo here
https://github.com/CursedFlames/BountifulBaubles/blob/master/src/main/java/cursedflames/bountifulbaubles/loot/ModLoot.java#L134

Duplicate entry names are invalid according to Forge, however for some reason it checks for duplicate names when entries are added via LootPool.addEntry(), but not in the constructor.
LootTweaker's internal mutable loot data structures properly enforce unique pool and entry names.

@Sunconure11
You can get worlds to launch for now by not editing minecraft:chests/simple_dungeon in your scripts, as LootTweaker only creates the mutable data structures for tables it has been asked to edit.
Alternatively, downgrade your LootTweaker installation to 0.1.6. It won't cause this crash because it doesn't include the internal mutable data structures, however it of course still has the bugs that were fixed in 0.1.7.