S2716DG, screen half blue

I have been using my Dell S2716DG that I bought new from Amazon for about a year now with no issue up until a few weeks ago. The monitor started appearing half blue when there's no display input (such as when the computer is sleeping), and very occasionally appears with the same half blue tint when the computer is on under certain circumstances.

I use this monitor with 2 different GPUs: GTX 970 hooked up to an Ubuntu 18.04 desktop with the proprietary Nvidia drivers installed. The second is an RTX 2080 on Windows 10. Both attached via DisplayPort, I switch between them.

I also use the monitor with a Nintendo Switch via HDMI occasionally.

But the issue still shows even if I unplug all inputs and switch the monitor on, so it is not an issue with display inputs.

Like I said, it appears when the display is on only very occasionally. On Ubuntu, I can see the half blue tint on the GDM login screen, but not once I actually log in to the desktop. On Windows 10, it appears in Overwatch.

This is what it looks like:

This is an up-close picture where you can see that it's actually vertical lines

I have tried:

1. Factory reset
2. "Reset" button on all individual settings
3. Hard reset (unplug and hold power button)
4. Driver update from the downloads tab on product page
5. Different DP cables (but, again, it appears even when no display input is attached)

Is there anything else I can do to solve this issue?