With this mod enabled, taking the last settlement of a faction gives 4 identical "subjugate" options with no art. Whenever you take the former capital of a destroyed faction, it gives the option to revive them as a vassal (also without art). With chaos dwarfs, this pushes the option to occupy as an outpost off the left edge of the screen.

I've narrowed it down with just this mod and it's dependencies enabled. If you want to test it quickly, start a Realm of Chaos campaign as Katarin and blitz the nearby Norscan settlement (should take 3 turns of auto-resolve). It seems like you might have bits of an unfinished or removed project in your files.

UPDATE: The bug is coming from the Druchii Overhaul portion of the mod. I was testing the component mods individually and found the problem originated there.