Wow, that's a stumper alright....Do you have a mag with a Lakeline follower to see if that might be the fix? With that many different mags all doing the same thing it pretty much eliminates a mag spring issue so I would first install a new recoil spring along with a good feed ramp slick up to see if that does it and if not try a Lakeline follower in a known good mag and if that doesn't do it may be time for a trip back to the mothership...Good luck....