Saw the same error where an enemy was graphically on a diagonal tile away from where it really was and I had to look at the map to see its true location, this time with a zombie in an open room so it doesn't seem to be geometry specific or enemy type specific. The only thing that's been the same between the two times I encountered the bug is there being a wall next to an enemy's real position but that's not much to go by =P
Another thing I've noticed is that rarely but sometimes you can see the outside walls of a room, at first I thought it was perhaps secret areas that could be accessed because I only saw a single tile of it the first few times but my last run I saw it for an entire corridor.