As precisely as I can recount the situation: I took the stairs up from the 3rd floor to the 2nd floor. Immediately, I encountered two Batties -- one in the tile immediately in front of me (right in front of the stairs), the other in the same tile as me (on the stairs). I killed the one in front of me, moved into its place, and turned to kill the one that was on the stairs. The first hit took it down to about 50% health; the second -- still a regular attack -- I assume would have killed him, but instead, the game froze. (My character's attack animation played out, the Batty cringed as they do when hit, but froze before damage count appeared.) I was fighting unarmed. My gear and skills had me dealing crushing, piercing, necromantic and asphyxiation damage; no knockback effects. I had no status effects active at the time. This is, of course, very difficult to reproduce on my end; this is the only time I've ever seen a monster spawn on the stairs. While I can't be certain that that was actually the cause, it did seem unusual, especially with it being in the same square as me.
Yeah, that one was pretty much caused by said batty getting killed on the stairs. That's because DoD has a problem with placing a body on the stars and goes to Albuquerque instead.
IIRC I also made a thread about a game freeze during an enemy dieing on the stairs, so they're looking into it.
Ah, you did? Whoops...I looked around before posting to see if this had been reported before and didn't see it. Sorry to re-report, then!
http://community.gaslampgames.com/threads/monster-dying-on-stairs.2269/ Just for the record, and for AmzRigh .