I'm working on a map for the first time.
I tried to find this issue on the forum but couldn't so I hope it's not a duplicate:
I've added several windows and doors around this map, and I can still add more. But in two rooms, on the walls facing 'south', when I place windows or doors, they don't appear and instead there's just a hole in the wall.
I can still select the door/window and move it around.
If I move it on a different wall it appears. When moved back, it disappears again.