Without knowing for sure, I would assume that the pins are coming out because the set screws that lift the FCG to tighten the pins against the receiver were not tight (or came loose).

I do concede that KNS pins or the JP pins that I used completely eliminate the possibility of the pins coming out, so in that respect, they are relatively cheap insurance and probably not a bad idea.

The KNS pins (at least one of them) is essentially the same as the JP pins. The anti-rotation feature however won't serve a purpose like I mentioned. The JP pins cost $10 vs $25 though...

Good luck in whatever you choose, and enjoy that trigger!!!