New
#41
Are you using any Nvidia Control panel settings? Let's abandon them to see if Nvidia bloatware is interfering as we see occasionally.
Manage your external monitor using only the Windows function for this on the Screen Resolution control panel.
Now type services.msc in Start Search box, turn off all Nvidia Services and set them to Disabled.
These should already have been turned off along with everything except your AV in msconfig>Startup and msconfig>Services (after ticking the box to Hide all MS Services).
After doing all of these reboot PC, then confirm again in Services.msc and msconfig that these changes have been made.
What AV are you using?