Fix for External Display Monitors Flicker/Issues with Dock (SP6)
Download and doubleclick the reg file and reboot... that's it!
https://www.reddit.com/r/Surface/comments/6uxfl7/fix_fix_for_external_display_monitors/
https://paulrobichaux.com/2017/10/02/clearing-the-windows-10-external-monitor-cache/
https://support.microsoft.com/en-us/surface/troubleshoot-connecting-surface-to-an-external-display-bc8f5121-a4cb-cf0b-5770-2df7a66a3b28#Setup