I built my first apartment last night and tested it out today. The lot zoned properly but three of my apartments, which have two stories with connecting stairs have their top stories "out of bounds". I've tried changing the stair type, and placing/removing walls and doors, but haven't been able to solve the problem.

How do I solve this problem? Thanks in advance.

Attaching some pictures, might be helpful. I can't see your problem right now.