Mac Mini Crashes while booting & gray screen appears

The system I'm trying to get working:

Mac Mini (Model: A1347) running OS 10.11.6

Symptoms:

When power button is pressed, Mac Mini chimes and Apple boot screen appears. The progress bar gets partially across (at least is 1/3 of the way & at most 3/4 of the way), there is a digital artifact stripe across the top third of the screen, then the screen goes blank (black) and returns to a gray screen (without chime, Apple logo, or progress bar) and remains there until forced to power down by holding the power button for 5 seconds.

Photo of the digital artifact (glitch) stripe screen is below:

Troubleshoot Attempts:

Booting from restore image:

I have attempted to boot to a known good restore image of OS 10.11 (from an external USB hard drive). Similar symptoms occur: progress bar to a certain point, screen goes black and returns to a gray screen without the Apple chime. The digitized glitch stripe does not appear before the black screen.

Booting from Safe Mode:

Holding the left shift button had the same results as booting from an external restore image.

PRAM & SMC reset:

No seeming affect on the booting problem.

Option + D Diagnostics:

Booting to Apple Hardware Test, and running extended test, showed no detection of failed hardware.

Target Mode to another Mac:

Booting the Mac Mini into Target mode and connecting to another Mac via a Thunderbolt cable showed the Mac Mini hard drive. Files were able to be accessed. An image of the drive was copied to an external hard drive using Carbon Copy Cloner. Booting another Mac with that copied image resulted successfully > OS, software, and files were all available after login. Booting the problem Mac Mini from the external (successful) image resulted in the same problematic issues described earlier.

Reseating RAM:

Same booting error. Glitch upper third, black screen to blank gray screen without Apple chime.

I'm at a loss for what to do next and am wondering if anyone else have seen these problems. I'm suspect of a graphics issue due to the glitch screen; yet Diagnostics did not show any errors. Any suggestions would be welcome. Please let me know if you would like any more info and I'll do my best to provide it.

Thanks,

Brad