I heard of a lot of issues too, but mine were just the usual "frankenmag" problems but a little more frustrating. I set up my body for giggles in a mechanical setup when I first got it (without the stainless washer) and it ripped, granted I never tuned the bolt or chrono'ed. Then I threw an emag frame on there and the washer in all hell broke loose; I had to modify an on/off pin after trying all the sizes, I had to use a custom length spring cut down by hand, and finally it took me forever to get the frame to work both electronically and mechanically.
Not "manufacturing defects" in my eyes, just "frankenmag" issues. When you've got parts from all different sources there will be tolerance variances. I've seen (rarely) those mags made out of a parts box that just won't shoot.