I think the issue might be the one I mentioned then, PUBG reading generic UE4 files. Do you have a folder under %LOCALAPPDATA% called "Unreal Engine" on the user with the issue?
If so, check if you also have \Engine\Config folder under there, and in the Config folder a UserInput.ini file (so %LOCALAPPDATA%\Unreal Engine\Engine\Config\UserInput.ini).
If you do have this file, it would be very nice if you could PM me the content.