I had the exact same problem. Vanilla game. Same apartment. Toddler beds placed in the same place.
I have 4 toddlers. The first born is a single, the other 3 are triplets. It's a challenge to keep them all happy and by the time I get them all to sleep I usually save and turn off the game because I need a break. Unfortunately it seems I can't do that anymore. Every time I load the game again they are all awake and angry, usually standing to one side of their beds. The toddler currently stuck in with the elevator shaft (see screen capture) has been stuck there multiple times.
I've found traveling somewhere like the park with the child gets them unstuck and when you travel back to the apartment they are in the usual place in front of the elevator and free. This is a bit easier than moving them out and back in but is only a temporary solution. Can anyone clarify for me if moving them out and back in permanently stops the "sleep teleporting" issue or not?
Thanks