Have not been able to pin down the reason for it, but sometimes the Move Window to Next Monitor button, in the top right of the window disappears, regardless of the app/browser I've opened. So I logout/reboot several times and it reappears. Then a week or two later it happens again. It's not a big problem but it's very annoying. My settings are never changed in the app or my machine and my WIN 10 Pro updates are current.