Had four 20 rounders out yesterday and had multiple problems.
To start, the mags need a good slap to seat on a closed bolt and pretty consistently multi-fed and jammed on each mag of ammo.
The kicker was that I could only fire eighteen of the twenty I loaded each time. When looking into the receiver through the dust cover it was obvious that the bolt catch was engaging with the follower not allowing the rounds to raise high enough for the bolt to strip them off.
After tossing the mags to the side thinking my rifle was the problem, I started using 20 round aluminum GI mags and did not have one hiccup at all, rifle ran perfectly mag after mag for at least a hundred rounds..
When looking at the mag from the rear, the follower seems to be at a slight angle from left to right and is a bit sloppy from front to rear when jiggled with my finger.
For what its worth, the mags are at least a year old and are not using the anti-tilt followers.
Could this be a worn spring and follower problem?
Update: I'm an idiot. Upon closer inspection with a flashlight, the problem had nothing to do with the bolt catch, the last two rounds consistently come up at an angle, rear lower than the front. I dis-assembled the mags and they're clean and all the plastic seems smooth, so nothing's binding. What's the problem here?
Update: Spoke with tech support and was instructed to explain situation via email, received a reply and problem is being resolved.