I've also been wondering what triggers it, but I can't find a reason. Nothing crashed or anything, it just happened.🤔 I kept my save files, but everything else disappeared. It's so sad, because I absolutely love the game.
I also encountered the same problem twice... my advise is to make a copy of the persistent file. From what I heard that's the file that holds the cgs, etc
The persistent file will increase in size as you unlock cgs, etc. so remember to save/resave that copy constantly. I myself always update the file (actually you might as well save the whole saves file in case the saves disappear too along with the persistent file) after every play, just in case.
