So, I was stupid enough to start a megafort on first release of 0.40, which I've carried through to 0.40.8 (So this is likely the cause of this problem.)
Anyway, I built a stockade of wooden walls, on top of which I ran a ring of fortifications & floors for my archers. With earlier versions I had a problem where if I cancelled/suspended a fortification build it'd be miraculously replaced with a fortification made of the same material as the wall directly beneath... which I could not deconstruct, remove or change in any way.
Fortunately, later builds fixed this.
Now I have what I think is a related problem... with building walls on top of walls.
In particular, I have two squares in which I cannot build, the job always being cancelled with "creature occupying square" msgs. The builders are NOT the culprits; they're standing in adjacent squares. I've even built alternative floors for them to work from and (r)estricted the original 'standing spot.'
I've also removed all nearby constructions in the X, Y & Z axis, then rebuilt them only to have the exact same problem.
Experimenting, I found I could build up/down stairs above, below and
in the problematic square(s). I can even build fortifications there; apparently it's only walls that will not construct in these spots, even after deconstructing aforementioned stairs/forts/whatever.
Of course, for the sake of OCDness I
have to have walls there...
Any suggestions or ideas as to what could be causing this?
(Besides starting a new megafort, that is!
)