When F10 is pressed, an error message 'SetDisplayMode' appears.
FIXED: It was a resolution problem. Apparently 16:9 ratios are a no-go
When you say 16:9 ratios, do you mean ones you actually have, like 1280x720 or 1920x1080? Your game could be at 16:9, but as long as your monitor supports the resolution your game is in, it should just switch. Anything else is a bug.
Also note that running the game at 2x size in the config settings will use that double resolution. So a 320x240 game would run at 640x480 fullscreen with 2x on.