A few years ago when we had wide spread power outages due to ice storm, I was running the house on a portable generator (through a manual transfer switch). One time when the generator ran out of fuel, I heard the generator sputter a bit, knew it was likely running out of fuel, then as it quit I heard a pop come from various locations throughout the house. Every one of my P&S GFCI receptacles had tripped. Probably some inductive kickback going on there I would guess. But I have had very few issues of tripping these receptacles. Did try an occupancy sensor switch in bathroom in my shop one time, was supplying T8 electronic ballasted luminaire. It would trip a GFCI receptacle in the area that was on same circuit but the load in question was not connected to the load side of this GFCI. Would not trip every time, but did trip quite frequently. I don't know why it only tripped when using that occupancy sensor, same light had been there a long time with no issues and no issues after going back to a standard switch. - Again a P&S GFCI. Have had very few cases otherwise where the trip reason was unknown.