Yea. The game really needs to let us adjust FOV for different camera states, aiming down sights, when entering interiors, when drawing out weapons etc.
All this automatic back and forth auto-fov-adjusting is sometimes quite annoying.
I fixed the issue with turning on the custom FOV locking up the game.
I moved the fix to another folder (from my documents to a temp folder) and ran the progeam as administrator.
checking the 'always run this program as administrator' box didn't work, it still locks up the game but manually runnig the program as admin did work.
Thanks rose for this fix, I'm still hoping for a FOV fix like I had for GTA 5 at some point where I can set different FOV's for aim down sight etc. but in the meantime this makes the game far more playable in first person.