I never finished my story on the tripping GFI. We had a rainy night while on our trip to Oregon last September. My new GFI breaker wad tripped and would not reset. I borrowed my wife's hair dryer and began systemically drying each of the six outlets on this GFI circuit; outside, fridge, bathroom, etc. The last one I dried out caused the GFI breaker to stay set! Bingo! It was the outlet under the rear bedroom window.
I found water in the rear window frame with a clear path inside. I got out my trusty Acryl R and sealed seams around the window frame and end cap. I also cleaned and inspected the window gaskets. I suspect one of my rear clearance lights was leaking too. All sealed up now.
We had another rain event on our trip and the GFI did not trip, although it was not a heavy downpour. The bottom line is a rear window area leak was dampening the 120v outlet in the bedroom causing the GFI to work exactly as it is designed to work.