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Weird issue with second display


Jun 3, 2015
My second display shows me this:

Screen Shot 2018-06-16 at 9.10.58 a.m..png

It’s like a “ghost” app or something. I suspect something running without my knowledge.. If I open a window on my second screen, it goes on top of that line (so it’s not a monitor issue). If I change resolution or display rotation from settings, the line stretches or rotates accordingly.

I’m not familiar enough with Apple’s processes, in Activity Manager, to know what’s supposed to be running and what’s malicious, if anything.

When I close my MBP lid, so it displays everything just on my second monitor, the line isn’t there.

It was there on High Sierra and still there on Mojave, so I ruled out OS issue.


Ambassador Team Leader, Senior Moderator
Jan 8, 2012
I assume the display settings are set accordingly. Is the resolution set to "scaled"?