Hi - Did you ever manage to fix this? I have a similar problem which also occurred in Dec 2021, no problems to that date 700+ hours (and playing since the series since OP Flashpoint 20+ years, so it has always been a go to game!). I tried some similar fixes, but nothing seemed to work at the time.
I figured I'd leave it for a while and see what happened with other updates, and have been travelling anyway - so have been away from my PC, but just tried again today after updating windows, graphics card and ARMA and no change.