S2716DG, Flicker and Text Graining

I have an S2716DG that I've had for just under 3 years, and it seems it has just developed a problem. I suspect it's a hardware issue, but thought I'd try asking here before trying to return or repair it.

The first issue is a full screen flickering and wobble, kind of similar to a CRT wobble. There's some horizontal banding across the screen, and also a pulsing you can see down at the pixel level. As an example of the latter, the horizontal lines seen in the icon for a text document will show as lines, then swap to showing as a series of dots, then back to lines, on something like a 1 second cycle. This flickering seems to be related to both the refresh rate set for the desktop and potentially the temperature of the monitor; the flickering is seen worst at 60Hz when the monitor is freshly switched on, and worst at 144Hz once it's warmed up.

For the second issue, text in the upper 2/3rds and left 2/3rds of the screen can show as grainy or badly formed. You can still read it, but it looks like the sub-pixel shading is misplaced or similar. As a concrete example, the "File, Edit, Desktop, Help" text in the nVidia control panel window shows perfectly on the far right of the screen, but on the left of the screen, the interior of the "e" characters shows with darker pixels than it should, almost looking filled in. This effect seems worst with thin black text on a white background.

Other info:

• Monitor is connected via DisplayPort to a GTX 1080
• If I run the monitor through the HDMI out of my laptop, I can't really see the flicker, but then it's only running at 60Hz; I haven't yet tried that when the monitor is cold and the 60Hz flicker is worst. I do still see the positional text graining regardless of which PC the monitor is connected to, and what input is used.
• I tried running a different (4k) monitor through my PC with the same DP cable, and that looked perfect, no issues.
• I tried removing the power lead from the monitor for ~10 minutes, no change on reconnecting.
• Tried removing all USB connections from the monitor, no change.
• Tried factory reset of the monitor, no change.
• The issues both show up on desktop and in games. Doesn't seem application related at all.
• I tried the monitor self test mode and might just have been able to see some flicker on the grey screen, but I feel this isn't the kind of issue that would show up on flat coloured screens.
• I was running the most recent nVidia drivers when I first saw this issue, but rolling back to the previous drivers didn't change anything.
• Turning G-Sync on or off on the nVidia control panel doesn't change anything.

Thanks for any suggestions of things to try!

Dave

Edit: Got some captures of the text issue; only phone captures off screen, but note how inconsistent the shading is in the text from the left of the screen, and the dark blobs top and bottom of the a,e and s characters. From the right side of the screen, everything is much smoother.

Section of text captured from the left side of the screenSection of text captured from the right of the screen