Turns out it's not fixed, it shut down again during Crooked Fingers tonight
Frustrating! That really stinks. A few thoughts...
I'd be very surprised if Grace didn't fix the unit, given their consistently outstanding customer care and quality service. It certainly could happen, but I'd bet against it.
Do you know to what voltage Grace calibrated the low battery indicator and auto-shutoff? The correct value depends on the battery to be used. Did they know you planned to use the V2 with your Tekkeon, and your Tekkeon's voltage?
Did you, by chance, send Grace your power cable and battery along with the V2? Or just the V2? Wondering if they tested it with their or your cable / battery. If they tested with their own, it might be time to re-visit your power cable.
Out of curiousity, from where do you get your power cables? Were all the power cables in play during powering problems from the same source? Earlier in the thread, you said the V2 worked fine with a borrowed power cable & battery...and it seems likely the borrowed cable was from a different source. Maybe you have a bad source for cables?
FWIW, my money's still on the power cable.