It could be a problem with the slide lock lever screw/washer/spring. DON'T OVER-TIGHTEN... steel screw in plastic thread! Use Torx#6 driver. The spring's forward coil holds the lever's pin in place by resting in the pin's detent. The rear free arm of the spring should lie on top of the shelf on the inner top of the lever to hold it down until the spring in the empty magazine pushes the follower up to engage the slide lock.
Videos on YouTube:
https://video.search.yahoo.com/searc...0&action=click
I hope that this helps a bit. I've had similar problems and found that the lever was coming out a bit and causing problems.
Wynn
USAF Retired '88, NRA Life Member. Wife USAF Retired '96
Avatar: Wynn re-enlists his wife Desiree, circa 1988 Loring AFB, ME. 42nd BMW, Heavy (SAC) B-52G's
Frédéric Bastiat’s essay, The Law: http://mises.org/books/thelaw.pdf
Thomas Jefferson said
“A government big enough to give you everything you want, is strong enough to take everything you have.”
and
"Peace is that brief glorious moment in history when everybody stands around reloading".