I bought a BCA 9 mm upper (like a fool) several years ago. I got better reliability from a straw and a chewed up nakkin' back in the 8th grade when I was into spitballin'.
There was a recall for just what you described. I "think" it had something to do with the magazine or follower. If you have one of the older G42's with that issue and take it to Glock they will update the mags.
If you want something a little easier to carry but very similar, check out the SIG M11-a1. Holds 15 rounds and has the same coated internals as the MK and comes with nite sites and SRT. I love mine.