Which was driving me crazy, each time, I thought I figured it out, then it happened again. This time it just happened two days ago. Let me write down the details and history, and someone may give me some advice, what I shall do. Thank you !

This GFCI is located on garage wall, it controls: a garage wall outlet plugged by sprinkler timer, two bathroom / front outside foyer wall outlet, back patio / attic/ one hallway closet/ a living room shelf light. It started two years ago, when I had my roof replaced and they removed the back patio light fixture, the GFCI tripped, later I found out the fixture was deteriorated over time, water could get into it, then I replaced the whole fixture and sealed it well. GFCI was reset. It was working a little while, all of sudden, one day, GFCI tripped itself, I could not reset it, no matter what I do, I went ahead to replace it with new, still could not reset it. I gave it up and lived with it for a while.

About 4 months ago, I need to repair my sprinkler, I found if I unplugged sprinkler first, I can reset it, and plugged back, everything was good. They fixed the sprinkler leak etc, and this GFCI was working properly, you can use receptacle Tester to trip and reset it. So, it has been good for last ~4 months, yesterday I want up attic to clean up junks, when I turned on attic light, the GFCI tripped, btw, it was good during last 4 months because I used this lights serval times before. I thought it was a bad bulb or similar problem about sprinkler plug, but, it was not, I could not reset it again by either unplugging or remove the bulb.

The wired thing is, even though you could not reset it right away after it tripped, you can reset it after the GFCI was "resting" a while, like a few hours. I tested twice it was like this, ie, after it tripped, you could not reset it, but you could reset it after a few hours, and it would trip again when you used the attic light. This drives me crazy, what I understood is: if there were ground default, you could not reset it until you fix default. How come "resting" it could allow it to be reset, and it tripped again if you used its downstream power, in another words, even the default was there, you can reset it if you let it "rest" for a while, but you could not use it since the default was still there ?

Please anyone help, give me some clue what this crazy GFCI tripping is about ! Thank you so much

Jim