"Phantom" Ceiling Plane

[coogan]

Is there a clue that I could use to detect this kind of condition? I am working on a plan (of which that "test plan" was a study) that is considerably further along (and more complex). It likewise has an open polyline (I keep getting the warning), but I have no clue where to begin looking in order to fix it. It seems impractical to delete and recreate every wall in the plan, one by one.

By and large, curved walls are the hardest elements to place and size correctly. (They will also lengthen rendering time considerably!)

Thanks for your help.