I have recently been "remodeling" my vault, removing rooms and putting in new rooms so I could be better organized.

In the process, I added a new 2-room Athletics Studio, then upgraded it. After the upgrade, all the Dwellers in the studio disappeared, and then I found them wandering around the vault, going vertically through the room below's ceiling, up to to the room I upgraded, then back through the floor again.

I have since fixed that problem by removing that Athletics Studio and putting a new room in. But I wanted to report the issue and see if anyone else has seen anything like it. Perhaps Bethesda can try to replicate the problem.

Try searching throughout the forum like I did, maybe.

http://www.gamesas.com/topic/1527878-my-people-have-been-flying-through-floors-and-ceilings/

For some reason, I can't seem to get the search results to work for me. I searched for "ceilings" which should have took me to the same post you linked to, but I got no results. Weird. Thank you for the pointer. I must be doing something wrong.

Same issue here.

I built a second room to upgrade the (A) of my citizens. When I finally upgrade it, they vanish. I found them in my first room of the same type.

If I set one dweller to the second room, he runs vertically and seems lost. At least, they all go to the first room (but can't train since they are more than 4 in a 2 cases room), are they confusing the room ? (considering the 2 rooms are the same ?)