S2721DGF, crashes, struggles to boot

I have had two new Dell S2721DGF monitors for less than 24 hours now and one has become completely unusable. To troubleshoot I will try to describe accurately what I am experiencing below. 

This morning when I booted up my PC, one came on fine, the other remained black although the power button LED came on. Every attempt to use the buttons and joystick to bring up the OSD to change inputs (or do anything at all) failed. The screen remained completely black. Even pushing the power button did not work, the LED remained on as if it was stuck on. I even unplugged the DP video input cable, still black screen. Again I tried to bring up the OSD and could get nothing. 

Next in troubleshooting, I unplugged and plugged in the monitor power cable. This saw a change, the screen booted up to a Dell logo in the center and an AMD Freesync logo in the corner. These logos lasted a moment or two before there was a screen flicker and then it went back to black. A few more moments passed and the logos reappeared, flickered, and then black. The sequence looped a few times and then remained black with the power LED remaining on. Again I could bring up no OSD.

Lastly, I repeated the unplug-plug in a few minutes later after Googling for known issues with the Dell S2721DGF (found nothing, too new). This time I saw an OSD and then even my PC desktop(!)...for 30 seconds before it went back to unresponsive black. I have replicated this sequence a couple of times now as well. I boot by unplugging-plugging in the power, see my PC desktop appear, watch it disappear soon after, and then the monitor is unresponsive. 

Help!

To rule out the obvious, I've also tested another completely different monitor with all the same cables and my PC is NOT the issue. This is isolated to one of the Dell S2721DGF monitors