All right, exclusive of inductivity or capacitivity, this may just be the Occam's Razor
solution to the problem (and I'm not talking about "operator error" thankfully).
I'm always happy when I'm a step (okay, a half-step
) ahead of the suggested guidance. I can't refute the grounding issue (back to the main breaker panel), but when we recently had a licensed electrician come in to energize the subpanel I installed, he pronounced my work to have been "just fine", and all the existing electrical was all in compliance with local codes. So, I doubt this is a grounding issue, reaffirmed even further below.
I also re-checked to actual live (hot) black wiring, and confirmed that with my voltmeter - so the wiring to the switch, black-to-black and red-to-black is exactly as the manufacturer specifies.
To better test the timer, even though it is currently set on the minimum duration (15 seconds), I ran an experiment, to see if the switch would ever
actually cycle the lighting circuit off automatically. And it did. At some point, in about a 7 hour time span, the switch did cycle the lights off, and when my wife entered the room last night, the lights did come on (although that startled her - since I forgot to tell her I had installed the switch).
Note to self:
Inform wife of all future electrical upgrades to avoid domestic unpleasantness.
So, the switch is working correctly, although we have no clue about when the lights actually cycled off (I suspect it was much longer than simply a little while
beyond 15 seconds . . . .). I wondered whether adjusting the Lighting sensitivity switch might do something (prevents lights from coming on when the room is lit - naturally or artificially). I can't imagine that's the problem, since it set at the absolute minimum setting). Is the solution here that we have faulty timer electronics, and that this is a merchandise return back to Amazon?