There are no moving parts on the back to go out of alignment.
I may be the slots are worn enough to not fully engage the locking prongs.
It's not hard to swap the plates from one back to another if you want to check the back. No there's nothing to pop out and go into the dimension where all the lost socks go. Take care when putting it back together, I don't remember if the light seal for the dark slide is loose or not.