Yes, I have had issues with gen 3 pmags not locking in at all. They have a chunk of plastic on the back side that seems to hit the bottom of the magwell. Gen 2 pmags i could get them in fine but they wont drop free. I couldn't get my Tapco mags to lock in either as they were catching a little lip of the upper where the upper and lower meet. Also IMI 10 rounders are pretty tight. the old ATRS mags fit great. I haven't tried any steels mags but sounds like they work fine for most guys so I have some coming.
I think someone was going to send ATRS some magazines to test. Not sure where they will go from there.