ToME: the Tales of Maj'Eyal

so I was playing a dwarf adventurer on insane roguelike mode using the following addons:
stone wardens
orc breeding pits restoration
item vault(which everyone who donated has anyway)
Dwarven Adventurers, which allows dwarf adventurers to get stone warden talents, but only if they have the stone warden addon activated are online and are a donator

I really doubt any of these addons matter regarding the bug

I got the squadmate achievement for the first time on insane roguelike difficulty, and yes, that was hard, even as an adventurer

after getting the achievement i headed back into Escape from Reknor to clear the place out
I immediately saw Norgan exactly one tile away from the staircase to the Iron Council, northwest of the staircase; there were 0 tiles between him and the staircase; and no matter where I went, he didn't do anything

I cleaned out the rest of Escape from Reknor, then I went back and decided to do one of the following things, (I forgot which):

move onto Norgan's space in an attempt to bump him somewhere else, and then move to the stairs leading to the Iron Council
or
move onto the stair tile leading to the Iron Council, and then onto Norgan's tile
the save is not still active

the end result is that the tile Norgan was on was occupied by me, and the stair tile was also occupied by me, and that the real me was on Norgan's tile

I moved from the tile and was able to go wherever the hell I wanted... except the stair tile that fake me was occupying
there was nothing I could do to move him, not even Willful Strike could move him
also notably, the Rod of Recall didn't take me anywhere, so I had to go to task manager, alt+F4, and start again from an earlier version of the save; later that character died and i made a new one with the same name

I have also received this bug. In my case, it was a Dwarven reaver on normal roguelike. The only addons I had in common with Zeyphor installed are the donor ones (stone wardens and item vault). I can also confirm that this bug was in the game before 1.2.2, as I lost a character to it some time ago (not sure exactly when, but I think it was before 1.2.2). Notably, also, the two copies of me shared resources and status, so using offensive abilities on the me on the stairs damaged both of us. Another thing I tried was going up the stairs and back down again. This did not work.

This has been around a little while. Each actor tracks where it is standing, and each map square tracks what actor is standing on it. This bug happens when a map square still points to an actor that has since moved away. The result is not actually a clone but more like a wormhole. If you attack that square, you hurt yourself because that square is pointing at you.

I added a clone-killing option to my Bosses Gone AWOL addon to deal with this situation. It doesn't prevent the bug, but you can remove these misbehaving references when they happen.