I work on Ubuntu 16.04 LTS on HP EliteBook 840. The notebook is connected to two external monitors using VGA and displayport 1.2. After disconnecting external monitors windows from screen connected by displayport are moved to laptop's screen. The windows connected by VGA are not visible because they are still in "old" position.
I believe that something is not refreshing because after opening display setting I see that whole screen is refreshing and I see the windows again.
Thanks for any clue.
Best regards, Adrian