To get back to the Kel-Tec S2K, I have hand one since 2010. I love the little gun. I don't have a high round count (maybe 500 rds) through it, but so far it's been 100%.
I have a carbine in all but one of my pistol calibers, including a Marlin camp9 that has been modified to take Glock magazines. the S2K holds it's own. The folding feature is what makes it work for me. I took a HP 17" laptop computer bag and made a good little gun bag.
They have a life time warranty for the original owner, so if some one is having issues send it back to them. From my experience Kel-Tec factory service is pretty good.
I understand we are all different and not everything works the same for each of us, and that's cool. But the little rifle works well for me.