what are specs of the PC?
What monitors? what resolutions?
I assume those details might help figure it out.
looks like it started that bug in win 10 1803
https://answers.microsoft.com/en-us...ns-black/81f524ef-9076-4154-bdfd-2aa16f7a9a36
I don't think that applies to desktop though.
Does it show in clean boot?
Try a clean boot and see if it changes anything - make sure to read instructions and make sure NOT to disable any microsoft services or windows won't load right -
https://support.microsoft.com/en-au/help/929135/how-to-perform-a-clean-boot-in-windows
it doesn't remove anything, it just stops non microsoft programs loading with windows, easily reversed.
if clean boot fixes it, it shows its likely a startup program. You should, over a number of startups. restart the programs you stopped to isolate the one that is to blame.