drawing from wrong registry, how to fix?

This is an issue I've encountered a few times: 
Under certain circumstances which I'm having trouble characterizing fully, while processing a datapack, the game attempts to draw from the minecraft: registry even though as far as I can tell it is indicated that it should be looking in some other registry. If someone needs a more explicit pointer to when this happens, it seems to be associated with processing structures.
I've encountered this once before when setting biome tags that a structure generated in, and eventually worked around it by the terrible method of hardcoding an enormous list of biomes into the file rather than creating a custom biome tag.
This time it seems to have manifested while trying to find a structure:

java.lang.IllegalStateException: Unbound values in registry ResourceKey[minecraft:root / minecraft:worldgen/structure]: [torment:obsid_dungeon]
Probably I'm being stupid and there's a syntax error I didn't see. Anyone know how to actually fix this issue?

I will provide the pack to help reproduce momentarily.