They aren?t the only ones. I?ve heard stories of problems with the Beretta M9 that were caused by government contract magazines from Checkmate.
I actually have first hand experience with a couple of crappy Sig (Checkmate) magazines that caused me quite a few feed issues. The same pistol ran like a well oiled machine on the Mec-Gars- both Sig branded and non-Sig branded.
Same I've heard elsewhere, many, many times.
Now explain the logic of pairing a $900 NIB gun with Checkmate mags? You can't unless you're Ron Cohen genius.
I am curious who is making the OEM mags for the P320/M17/M18 though. They don't seem to be having these issues.