1) Kill a critter 2) Enter Pocket Dimension 3) Take 1 step 4) Return back to dungeon The dead critter will run its default animation cycle just once, then stops. Its tooltip will say it's dead, but also that it's trying to kill you.
I've actually seen this in 1.0.10 and 1.0.11 as well, when entering a dungeon level (e.g. ascend to level 2), so I don't think it's new.
You are probably right. The underlying defect hasn't changed. The Pocket Dimension just makes it occur more frequently.