I'm pretty sure it's due to specs of powder or just junk that gets down in there. I tore it apart last night and there was a lot of powder in there, good quality shells I guess. My concern is that I've never had this issue with any shotguns I've shot in the past.
To answer the question once you shoot 3, the safety is still on with the action open, from that point, Ive had it where no matter what you do, that safety is stuck on fire. Kind of scary actually.