Let me tell you a little anecdote.
Since few days I had a strange behavior on my screen. After opening, closing, but especially after moving windows, white glowing lines remained. For example, the picture below (cannot be captured by screenshot) after moving Galculator back and forth. When I moved the window over the line, some or all of the it disappeared.
To rule out a hardware defect, I used a tool to test the VRAM and the monitor test page from Eizo. No result, no errors.
Then I replaced all the cables and changed the connection from DP1, DP2 to HDMI1, HDMI2 and vice versa. No improvement.
Next I looked at the power supply and connected the computer and monitor to different power circuits in the house. No result either.
Then I had the idea of changing the display frequency in the system settings, but no result there either. Doing this I noticed the scaling. I had it set to 85%, because even with my blind eyes, the windows were all way too big for me. So I set the scaling to 100% and wtf 
the problem disappeared.
Now I’m sitting here with one laughing and one crying eye. After hours of searching on the one hand I’m happy that I don’t have defective hardware, but on the other hand I have to look at these monster windows at 32" and WQHD resolution.
Have a nice day everyone.