I can usually just go back a few steps to fix the glitch but when I try to merge them again it will corrupt the same way as soon as I press play. There are no bones and adding them didn't help. I've also ensured manually that each object's origin is at the same coordinates. Just now, I opened the file and I've found it's corrupted again. I've been trying to figure this out for days but it takes time because I keep having to remake the objects that get corrupted. I'm trying to add a white trim around the door and it's worked on only one of the two. Sometimes it doesn't corrupt right away. I can play the animation endlessly and move on to play with the rest of the design. I might even be able to continue working on it after saving and reopening it before it does this. The animation still works fine though...
The one that isn't corrupted has a few more vertices because of the lock and knot in it but it doesn't account for the number lost between the doors.
I had this one working for a while and would like to recreate it.