Full screening game window doesn't actually become full screen

When opening the game through Steam when windowed, BeamNG begins as a window, not a full-screen window, so I click the maximize window button. A sliver of the background is still showing when it goes full screen. To fix it, you have to window it and then full-screen it again.

 

Use Borderless, I use it in every game and it's less buggy than fullscreen.