Took the misbehaving one back to the retailer and exchanged it. Installed the replacement: identical behavior.
Swapped it with the other GFCI to see if the problem would follow the unit, or stay with the box. *Both* units work properly.
Speculations as to what's going on? I'm at a complete loss to explain this.
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?