When I start the game it appears on the second (wrong) monitor, after waiting for the Bohemian logo to appear, I alt-tab out of the game, open the gnome shell and move the window/game to the correct screen and switch back into the game. After the game has fully loaded I can operate the menues normally. If I then alt-tab out of the game again and back in, menues will not respond to mouse clicks.

It's worth noting that the screen the game starts on has a higher resolution (1920x1200) than the screen the game should run on (1920x1080).

The game will still respond to keyboard input and if I started a campaign before alt-tabbing out I can still fire the gun, but I won't be able to operate the map for example. Or the inventory menu.

This happens on a amdgpu-radeonsi system with Gnome3/Gnome-shell and a dual-monitor setup where the game has to be moved to the correct screen by hand.

Also unplugging the mouse and plugging it back in didn't fix it either.