I and my friend entered the Police Station on Krasnostav and saw a corpse (or possibly a prone player) fall through the celing to the 1st floor. Wasn't possible to loot him. Suddenly he disappeared and fell through the ceiling down again. Happened like 3 or 4 times before he disappeared for good.

(That's all the info I have, we didn't bother looking more into it as we still weren't sure whether we're "alone" in the building).