Just bought a new Shield 45 from Palmetto State Armory and first time to the range with it having the same problem; mag drops on recoil when shooting with left hand -- not good!
Thinking that my lefty grip/finger was the problem, my first plan was to simply swap the mag release to right side and experiment; but then I was surprised to learn that the mag release is NOT REVERSIBLE on the Shield models.
So based on this thread it sounds like maybe the mag design is the issue. I guess I will call S&W and see if they can send me some new mags, or followers or whatever. Last resort maybe they will trade me for a new Shield 9mm model. Kinda sucks because this gun is super accurate and I prefer the 45. Actually very happy with it except the stippling is just a little too aggressive for me; oh yeah and did I mention that it drops mags...
Memo to PSA and any other retailer selling these DEFECTIVE MAGS; please read this thread!
Memo to S&W: why are you shipping these if they are defective, and where is your recall notice?