I recently noticed that some dead monsters in my game are listed as having 1 hp remaining. This isn't really a problem but it seems out of order and for all I know may be related to some other bug that is a problem. Attached is a screenshot.
I am pretty sure this is the same bug as the one where monsters slowly heal themselves, as I often observe the two together. They also briefly animate as if though they're alive after taking a stairwell to a floor with 1-hp dead monsters, and then get stuck in a frame of their walking animation but don't appear dead.
I can confirm the one hit point thing also -- I saw it this evening in an unmodded run. Not all corpses are listed with an hp, but I did notice one. At least in my game, it didn't seem to have anything other than a cosmetic affect.
This seems related to instances of things like monsters that have been dead for several rounds resisting or being haywired by ongoing effects like "on fire."
Fun fact: I put this bug in during one of the betas! I thought it was related to overkilling a monster, but never did quite figure it out. While this knowledge is useful, given that it's cosmetic, it might be around a while...