Bulkhead and door question - Cosmographer

I'm plodding on with Deckplans, thanks to Monsen and others, and have noticed that the door symbols aren't breaking into my bulkheads (walls?). They just sit on the bulkheads - see atached .fcw file - and I don’t know why.
Comments
Seems to work fine for me in your drawing, but notice this:
For stubborn walls, happens occasionally, I have to hide all but walls, and then use the wall cutting symbol. Then place the door.