Game keeps corrupting it's own files

I will be playing with a friends, when some part of my game will dissapear (such as my character model), then stutter, then lead to a crash.
if I try to relaunch the game after this it will tell me that there are corrupted files that I need to reinstall or repair.
Doing this makes no change...UNLESS i restart my computer first then do it, after which it will tell me that it needs to reaquire 3 files and once it's done it will work fine for a while before doing the exact same thing again.
I have tried running as admin, checking my hardware to see if that's the issue, changing settings in both steam and the game, clean reinstalls, the lot.

this is getting annoying, I just want to play with my friends.