After checking everything else on that circuit, I decided to take a look inside the GFCI outlet.
There was black residue inside the GFCI outlet. Some of the electronics on the little printed circuit had fried. It did not trip, it failed.
I can only conclude that the GFCI outlet failed in such a way that it activated the ground when it failed.
One thing I haven’t quite figured is, if this shorted to ground, and assuming a good ground to earth, why did the breaker not trip? Perhaps it could pass very little current, not enough to trip the breaker.
At this point, I will replace the GFCI outlet and call it good.
Wayne
