You can load the map attached, this seems to mainly be with staircases, that creates a crash.
Select the staircase and list FRONT" button.(oddly -If you click "Ignore' the editor doesn't close. So it isn't so severe you lose your work)
Display the LISTS dialog on the side, the brush order SHOULD change, at least I thought it would. This to show the change in the order of brushes in that list.
WHAT IS FRONT?
The manual tells what it is.
It arranges so that a solid made after a cut brush isn't cut into by the cut brush. Say you add a room after create the brush and decide to add a staircase or box from another part of the map. The newly created cut brush will wipe out the older solid box or stairs.
FRONT changes the order so that the selected object, if this case the stairs is move in front of the list.
Spiral Staircase map