Double hit instead of one hit

Hi
see picture below. By hitting “F” one time nothing happens. I have to hit “F” twice to the the result.
Any idea ?
Thanks a lot,

It will run the “windowed” command first, so If you are starting the game in windowed mode, you won’t see any different.

Yes of course, but this not my problem. Everytime I will switch the state I have to hit F twice.
Not only at the beginning of the level.