First thing I'd do is tear down the magazine; lightly lubricate the inside, spring follower with Breakfree, then wipe dry. If cleaning and lubing the magazine doesn't do the trick, then I'd use a buffing wheel on a Dremel tool (without any compound) and polish the feed ramp.
What ammo were you using?
Were all the problems with the same magazine?
Check this link...It's about the MK II but may help.
http://xavierthoughts.blogspot.com/2...ine-tweak.html