Fullscreen mode will not work, game defaults to windowed (solved)

I normally have the game running on fullscreen mode so I can turn the resolution down and have some hope of getting anything like ok performance, but today I had to tab out to go into another window and now even when I change the setting to fullscreen, it does so for a moment before going to a small window in the middle of the screen.

 

Whenever you do alt+tab or press windows key it goes into windowed mode. With borderless that doesn't happen.

 

oh i just reopened the game and the bloody thing works now
--- Post updated ---
ffs

Edit: no it doesnt the problem has returned

WHHYYYYYYY

 

Press Alt+Enter to go into fullscreen

 

Thanks! I'm gonna have to write that down somewhere...