Not sure if this is RotDG specific or not, but that event room with the disappearing walls once you get close enough? yeah, I had a set of upstairs spawn on a wall that disappeared as part of that event. The animation looked weird and it left a perfectly functioning set of stairs hanging out in the middle of everything. no crashes or anything though just... weirdness.
Hello there KotHN Yeah pal, nothing is going wrong or glitchy, thats how it looks like afterwards of the ambush event, but I do agree though, it does look weird and out of place, maybe if the stairs looked very damaged afterwards might make it look more fitting.