I just received a P12 purchased from TMR, and noticed the lower 20% of the display flickers!
I took a short 4-5 second video, but cannot seem to attach a video 
Being new to me, I did a restore to factory defaults, and also unplug / replug to the wall.
No change 
Would that be a known issue?
Is that a red flag for possibly a bigger issue in functionality?
ANY help is very welcome! 
Post the video on YouTube and then post the YouTube link here.
Here you go:
There have been issues with these screens in the past. Not a common problem, but it does happen. The screen on my DAC had scrolling lines, had to return the unit to PS Audio to replace the screen and controller. Done for free under warranty. I would contact PS Audio and see what they say. Since you bought from TMR I’m assuming this was a used unit. That’s not a problem for warranty as far as I know. They can tell you how long the unit has been in service and if it is still under warranty. I’m not aware of any user remedies, beyond what you have already tried, but don’t take that as absolute. Good luck!
Might be that the display itself needs replacing.