The mouse is a Logitech G502, the keyboard is an ADX Firefight H01 mechanical keyboard. The mouse's drivers are fully up to date, but there don't appear to be drivers for the keyboard.

As of right now, it's working, but it was working before and it still messed up eventually. We don't understand what's different. The only thing that seems to prompt it is alt-tabbing.

At the moment it's working fine despite our best efforts to try to re-create the problem, and we're just as puzzled as to why it's not messing up as we were to why it was messing up in the first place.

Our best guess is that the game thinks his mouse is a controller for some reason. He currently has "Enable Virtual Mouse" checked under gamepad settings, and we think that's why he's not encountering any issues.