Just had this issue happen again today in a very large level after having it not happen for a couple of months. Every single puzzle element in this level now needs to be recreated. It happened after saving everything, closing the editor, putting the computer to sleep and coming back after a few hours and opening it back up.
Seriously, this is a very important issue, and I assume that it’s hard to fix, otherwise it’d be fixed by now. But really, can we at least get some sort of status update on it? It feels obvious to me and a lot of other people that this issue is affecting quite a lot of projects and is becoming a major roadblock in trying to polish pretty much anything.