I know there is a very descriptive post about this issue. I had "survive 6 mole ray attacks" quest and they attacked an empty non connected part of my vault. Then when the left the vault crashes seconds after loading. I'm posting this in the hopes that an update will fix this if enough people complain about it.

Having this same issue as well. Game is unplayable. Only happened when they attacked a room only connected to an elevator. So when they go to despawn the game crashes.

Confirmed this issue as well, and reading a lot of posts elsewhere as well about "game crashes on startup" which mention a molerat attack being active in the vault. Any time the molerat objective is active and they despawn of their own accord, the game crashes.

Possible workaround that comes to mind but I haven't tried yet: canceling the molerat objective if it appears, or using a save editor to auto-complete the objective if you don't have a free cancel left for the day.

Can confirm that cancelling the objective prevents the crash (if you can get it in time). I couldn't get people into the room to fight before the crash so I don't know if that will work but worth trying if you can.

Shame to lose a lunchbox but at least I didn't lose my vault. Needs a patch asap though.