Erratic behaviour and (at least to me) unknown HUD in lower right corner of all of the ViewPorts in Rhino 6 SR32. The HUD is looking like this: 
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Nathan ‘jesterKing’ Letwory, McNeel - (Suggested Oct 2018) that it might be a ShadowPlay (Nvidia) thing.
Did you try turning that off? Or the equivalent for whatever the AMD solution is?
Hi Nathan. It’s from a client, so I will return with answer, when he get’s back to me tomorrow. He has a NVIDIA GeForce GTX 1070 (NVidia) Memory: 8GB and two monitors, so if ShadowPlay is at work, it might consume a large amount of the GPU resources for capturing the desktops of (2x1920)x1080px.
Rhino’s ViewPort feedback is extremely “laggy”/“jaggy”, like if you have selected a too large SnapSize.
No idea what that means for Rhino.
Solved! - Without uninstalling GeForce Experience/ShadowPlay
it is possible to change the HUD Settings with the shortcut Alt+Z. 
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Restart Rhino 5/6/7 after setting all of the four NVIDIA “HUD-Layout” functions to None/Off.
At least this is a good starting point before uninstalling the entire “GeForce Experience” 
Yep. It works. Thanks for pointing me in the right direction. Very odd ViewPort-phenomenom.