Disappearing floors in build

I’m having a similar issue. Noticed the date on this thread and others, wondering why the issue is still here? The way mine is different than others in this thread is the glitch just suddenly appeared. You may recognize the apartment, the room that’s floor is missing is largely unchanged, I think I only really moved around the door and shrunk the closet/hallway area. It was the first room on the second floor I redecorated, and in between the different rooms I went in and out of build mode/live mode multiple times and there were no floor issues. Even after I finished the entire apartment and took pictures, everything looked fine. It wasn’t until I left the lot (one of my sims got asked on a date) and came back that the master bedroom’s floor was missing. My thought is because the patio is directly below said room, the game removed the “ceiling”?

If anyone has figured this out or can put this in a more recent thread if there is one id really appreciate it, I love this family and I spent awhile on this build and id hate for all that work to go to waste. 

Edit - split from outdated thread, edited title to better reflect issue (Bluebellflora)