I had the same issue one 2 of my 6 mags. One of them seemed to work after a while, but the other one is really hard to pull out so I RMA'd it back to MidwayUSA where I bought it from. Try dropping it with a full magazine, if it comes out, just give it a while to loosen up over time, if it doesn't come out, I would consider getting it replaced.
this is a new mag.. it worked flawlessly the first 3 times i emptied it today when shooting,it would drop free, then i noticed it would not drop free when i reloaded it with 25 rounds is when i noticed it was splitting at the top.
i took it apart and spread the gap and put superglue on it, then clamped it together tightly.. its drying now.
Try this, un-screw your mag release about 2 turns, you may be to tight and thus requires a very solid press of your trigge finger. Depending who installed it at the factory, they may have done to many turns..
One of my Officers had an AR15 with the same issue, the builder of the AR went in way to tight and it would not even eject. It's treaded so it can be adjusted, so give it a whirl... if you get my driff... Good Luck.