I'm starting to think that my woes are due to the power supply. My two Rpi3's, one is a Cana kit and the other is a Vilros, both came with 2.5 amps / 5v power supplies.

One Rpi3, using the Vilros PS, doing 1090 duties, works fine.

Is the other Rpi3 that, no matter what PS i use, gives me an under voltage warning.

Guess I'm going to hold off for a while until I find a proper power source before continuing testing.

I do thank you, abcd567, and others for your help and patience.