In my first playthrough of 0.5, i couldn't go down the stairs to the cultists next to the first town, so i skipped it and went to other places.

I kept checking those stairs on my way back and forth around the starting area and could never get down them. 

Now i'm up at the forgotten catacombs under the cemetery. I've cleared the place out but i can't get back up the stairs. I suspect there's an enemy above them because i saw the red flashes from hearing them as i walked back toward the entrance. 

I've tried making a bunch of noise with skills to try to get whatever is up there to descend, but nothing is working and now i'm stuck :(

This is still an issue. If someone is on the other side of the stairs, you can get stuck with zero capacity to do very much about it. I have had multiple characters die just from being "afraid" of going down the stairs because there are people on the other side. What I would probably suggest is something like how this is handled in Caves of Qud, where trying to move down the stairs results in an attack against the creature blocking them, or otherwise a prompt that asks if you want to do so, shove past them, etc.

Thanks for report plaguevictim69, I'll patch it up in 5.0.1.

The issue will be resolved in v0.5.0.1, should be available in the next hour. AI entities got stuck on rotations when attempting to move between z-levels.