The cord was corroded at least 2 feet back on the neutral wire which I think was the lower wire when plugged in. And the corrosion was present across all the strands. The receptacle itself was fine but the wire lugs were loose. I was just going to replace the plug and socket but now need a new cord.
There was. a measurable difference in resistance so there was more corrosion to be found. I sprayed the new plus connections with BoShield and will do the same with the cord end.
It’s an easy thing to check with an ohm meter.