I haven't found a double post for this one either. I've noticed that if you try to exit a dungeon to anywhere not dmap 0, they do not work. However, if you make a tile warp, that can get you out to any dmap.
side warps for dungeons if not dmap 0
I don't believe this is a bug, I have many sidewarps used in various ways in my quest and they're all working as designed.
Please post a test quest.