Glad you got this sorted, your post really helped me as I have the same issue. Interestingly it's not on every GFI outlet so I never pursued repair, but I'm going to sell after an upgrade so I figure it's smart to fix it beforehand. I took the switch apart (a PITA) and it seems to have resolved it to a large extent. There's still an occasional trip but I think that's an aging outlet that I'll have to get management to replace at some point.

Now to relax, repair was a bit frustrating.

J