God have mercy. I have seen a bug similar to this as well. Typically when that happens, there is nothing you can do except load an older save. Worst case scenario, you'd have to restart the game.
For me, the worst thing I've seen was in the original Neverwinter Nights in the early 2000s. The friendly NPCs that could never attack you despite if you tried attacking them... suddenly always tried to kill me. Including this one person that was supposed to give me a quest in the sewers (or something) and I couldn't do anything. I ultimately had to start the game over, since you had to complete the quest, as it was not an optional quest.