https://bugs.winehq.org/show_bug.cgi?id=21158
--- Comment #4 from matthias_berndt@gmx.de --- I would like to point out that this bug is not fixed. I'm having the exact same problem running the Steam version of Hitman: Contracts on Proton 6.3. As soon as I switch to another window using Alt-Tab, the mouse buttons stop working. When I switch the resolution, they will work again. Oddly enough, even restarting the game (or the computer) doesn't solve the problem, you really need to change the resolution!