Steam: Controller not working anymore in Forza Horizon 4

So I've been playing Forza Horizon 4 for a while without any issues using a XBox One Controller via Bluetooth. First i used Proton experimental and later Proton GE. Absolutely no problem.

Now however, the controller is not being recognized in game anymore (the on screen buttons show keyboard keys, not gamepad buttons) and I can't use any of the buttons (except the screenshot one). In the Steam menu, the controller test settings, big picture mode etc. it works fine and its recognized normally.

I didn't make any changes (before it happened, now of course it tried a bunch of stuff) but I did upgrade the system normally.

Any ideas what might have caused this issue?