If it were a problem with improperly loaded mags, then you would most likely be having failure to feed instead of failure to fire. If it is ejecting properly when you pull it back manually, that is a pretty good sign that it got into the chamber correctly to begin with. Failure to fire is likely an ammo issue. What kind are you using?
“Some people are like Slinkies - not really good for anything, but you still can't help but smile when you see one tumble down the stairs.”
A gun should be a tool in the hands of a deadly weapon, not a deadly weapon in the hands of a tool.