I'm having a problem with a GFCI outlet faulting for no "good" reason. The run extends from the garage down beside the drive way, buried about 8" depth to a light fixture on a brick column near the street. The wire was 10 wire approved for direct burial. On the column are two boxes, one for an electronic eye ( dusk to dawn switch ) and the other is an outlet with a protective cover. I checked both boxes to make sure they are waterproof and not leaking. If I unwire the run that goes to this light, then I never get a GFCI fault. This same configuration is also in use on the other side of the drive, and has zero problems with faulting.
The only "thing" that I can think of is that somehow this wire that was approved for direct burial is somehow causing the problem. Perhaps there is a nick in the wire insulation that is causing the fault. It's most strange because sometime I'm troubleshoot the problem and be fault free for several hours. Then, other times, it will fault within 10 minutes. Both on the same sunny afternooon.