When we had problems with our semi-automatic pistols and AR15 pattern rifles, most times it could be traced to magazines, especially as relates to double-feeds. Occasionally, but rarely, little or improper weapon lubrication was the culprit.

I would try to determine if these malfunctions are occurring with a specific magazine or magazines. I always told my fellow officers not to fall in love with their magazines. They don't last forever and should be treated as a "wear" item. Consider checking the magazine lips for signs of damage or deformation. You might wish to consider replacing magazine springs. Cycling the magazine through loading/shooting contributes to spring failure. Contrary to what some espouse, I never found a quality magazine taking a "set" from being left "loaded". Instead it was the many loading/shooting cycles where the spring was compressed and then released by firing the weapon that led to its eventual failure.

I'm certain others more knowledgeable than I will be by to provide further information.

HTH.

JPJ