"Can't keep wall and floor joined"

[kate.morrical61357]

I get this error periodically when trying to attach the top of a wall to the underside of a slab, but I can't figure out what triggers it. The attachment works fine, I edit the slab, and then it doesn't any more.

Has anyone else seen this?

[scowsert]

I get this error periodically when trying to attach the top of a wall to the underside of a slab, but I can't figure out what triggers it. The attachment works fine, I edit the slab, and then it doesn't any more.

Has anyone else seen this?

I've seen it but am as clueless about it as you are.