Matches start with "Keyboard Only"

Since a day or two I am having this weird error. When starting the game, I can use my 8bitdo controller in the menus and when I start a match, the controller switches to "keyboard only" and as soon as the match is over, the controller works again in the menus.

It doesn't matter which controller I use, if it's via USB, wireless or bluetooth. Same error with each controller. Everything worked fine until today.