It sounds like that the problem is with the ammo and not the gun. The mechanism on the gun is machined and is consistent. If the gun failed to fire with one type of ammo and fired flawlessly with another manufactures brand, I would feel safe to say it was hard primers. Shooting paper with cheap ammo is one thing, but if the gun fits you and fires your choice of defense ammo, whats wrong with the gun?
I shoot PMC Bronze for target practice and carry 2 magazines of Fiocchi 90gr.XTP JHP for defense.