huh, that is bizarre, I was hoping it was a simple misunderstanding which is common in the forums but this sounds like a pretty serious bug
have you tried things such as reducing settings, running as admin, using the regenerate data.sav in settings? Beyond basic troubleshooting like that it could be a weird hardware limitation, the game is super unoptimized with demanding hardware dependencies and needs a fairly modern pc, i5+970 or better at least