This fix suggested in another thread worked for me when I tried it quickly just now:
Please open the ingame console and type:
I'll try it in a longer game tonight
@Uveso This seems to have fixed if for me in FAF. I'll try it out in a proper game tonight.
Yeah it's definitely related to the cursor. If you whip your cursor around you can effectively pause the game. Don't touch it and it seems to run pretty much fine. How annoying.