Just because some GFCIs are working does not mean a surge
could not exist. These GFCIs are outside. Using buried
wire? IOW if the exterior (exterior) GFCI made a better earth
ground than the central earth ground for 'whole house'
protector, then surge would also use GFCI as a destructive
path to earth. If mounted on side of building, then this
scenario is not so likely.

Operating temperature for older versions GFCI chips is
typically up to 70 degrees C. Chip consumes near zero watts.
IOW heat is not a likely reason for failure for those type.
Have not seen datasheets for newer type GFCIs. But then is
that receptacle getting so warm that IC would exceed 70 degree
C?

How good (and short) that that ground for the 'whole house'
protector. Is there any good earthing path via those GFCIs?
Perhaps are those GFCIs located on the far side of the
building?


Jim Thompson wrote:
There *is* a whole-house surge-protector. All the GFCIs inside check
out OK, so I'm guessing it's a heat issue only.