On Mon, 23 Jul 2018 18:05:42 -0700, Jeff Liebermann
wrote:

On Mon, 23 Jul 2018 16:46:17 -0700, wrote:

I do test most of the GFCI receptacles monthly. They always pass. So
I'll replace the two and see what happens.

This explains what might be happening and how to troubleshoot it:
https://www.fluke.com/en-au/learn/blog/grounding/chasing-ghost-trips-in-gfci-protected-circuits
https://www.fluke.com/en-us/product/electrical-testing/clamp-meters/fluke-369-fc
https://www.fluke.com/en-us/product/electrical-testing/clamp-meters/fluke-368-fc

Duz the house have aluminum wiring? I've seen similar problems caused
by aluminum wiring at a friends house:
https://www.eng-tips.com/viewthread.cfm?qid=199901
We traced the problem down to loose screws on the wall outlets and GFI
receptacles. Tightening everything down make the false trips
disappear for about 6 months, when they came back from the dead
initially on anything that drew high current. The owner then
tightened down the screws again, which again fixed the problem for a
few months. I think you can see where this is going. The aluminum
wires were being squashed by the brass screw and cold flowing until
flat with the added bonus of some galvanic corrosion in the bath and
laundry rooms. In the end, he installed copper wire pigtails and
anti-oxidation goop on all the outlets, which I think finally solved
the problem:
https://ask-the-electrician.com/gfci-outlets-and-aluminum-wire/
https://diy.stackexchange.com/questions/291/whats-the-best-way-of-replacing-a-plug-or-switch-in-a-house-with-aluminum-wirin
Thanks for the links Jeff. The house is only about ten years old and
was built for us and we are the only people who have ever lived in the
house. So I know the history of the house which helps. I'll check out
those links today.
Eric