I bought the UP2715K monitor along with a Dell recommended Nvidia Quadro K4200 GPU and never encountered this problem on two different Z170x motherboards. I'm now seeing it on a third, new motherboard. The problem is documented by Dell (below).

All I have to do is switch off the monitor and switch on again or wait till the OS has booted and THEN switch on the monitor but it's still annoying for such an expensive monitor/GPU.  I have clean installed the latest version of the graphics driver but it made no difference.

Anyone else had this problem and if so, have you found a more effective solution for it?  Since it never happened on my two previous motherboards, I am hoping there's some config or setting I can change on this one.  I tried an Asus Turbo Series GTX-960 4GB graphics card and the problem didn't occur but then I had the other documented problem of no access to the BIOS during boot up. (sigh!) I also put the Quadro GPU into another PC and the problem didn't occur.

I wish Dell could have fixed this before releasing the monitor.

Gigabyte Z170X SOC Force motherboard,

Intel Core i7 6700K,

16GB Corsair Vengeance RAM

Nvidia Quadro K4200 GPU

The Left and Right side of screen do not sync/align

Your monitor may not have recovered properly after your PC wakes from sleep/hibernate, DC power cycle (pressing the monitor’s on/off switch), or switching between different resolutions. Symptoms include: Split screen, Left and Right of screen not sync, stretched or garbage image, scrolling image on screen.

Workarounds

• unplug and plug back in the AC power cord from the display.
• If using NVidia graphics card, update NVidia graphics driver to R347.88 or later.
  • NVidia drivers download page: (http://www.nvidia.com/Download/Find.aspx)
  • Always install the driver with Clean Install. (During installation process, select "Custom" install. Select the box that indicate "Perform a Clean Install").