I had this crash happen on 3.1.3 and now 3.1.4. First one was going up from dwarftown with waldenbrook following you, now going up from VD:7
the carpenter following you. There is an altar on the level. To reproduce the bug, from save fight the invisible stalker to get to carpenter, then lead him up the stairs.
Going up stairs without him following is just fine.

ADOM crahes with a small pop-up "There is no altar on this level", clicking that gives "Save directory overflow" or something like that.

https://drive.google.com/open?id=1pQ...h9SE7kh0cx_8IK