From what we can tell, because this seems to happen only when people quit the game, it might be an issue with the save writing process at game quit. It seems the game wipes the old save, starts writing the new one, but the game closes before it can finish writing so you end up with a wiped save. Fix is to always backup, but you can also manually save and then kill the process so it doesn't try to overwrite
Have also sent haxus an email about this since it's extremely severe
Have also sent haxus an email about this since it's extremely severe
What even