I was able to play with my friend for about 45 - 50 in-game days and then he suddenly started getting error codes appearing on his screen. In order not to impact his gameplay, I left him to do his own thing and I stopped playing. I finally joined him again today, 5 months later, same save, and he once again got the errors on me joining. Zero issues in the intervening 5 months. Vanilla game on both sides, both ran the file integrity and reinstalled. Nothing changed. We, literally, did nothing abnormal during our game time.
Here's my output log for this session. I'll try to get his later since I'm sure that would shed more light on any potential issues.
Any help would be greatly appreciated.
Oh, and we know to press F1 to close the error window, but it simply reappears.