If it is happening specifically after a long rest, you can try using a supply pack rather than food - that fixed it for me. Something about how food has been coded seems to be crashing the game right now.
I tried this, and concluded that if I give him the flask when in camp and then rest with a supply pack, the game allows me transition back into the world without crashing, which is great. But as soon as I save the game any time later, it will crash again with 100% certainty, despite what resources I used for resting. Very mysterious one.
