yo jec,
besides of my byakhee-texture working backwards now (yea it walks with ass forward), there's a sealed coffin with a frenzying vamp in a crypt that can't be opened.
i even put a sleeping spot on the ground and changed it into prisoner and that affected the coffin too, but only as long as it was placed.

a dev mode option to forcefully open coffins could be a hotfix until you figure out how that's caused at all ;)