Hi, I have bought new XD9 4" recently from a local gun shop. It came with 2 magazines, but I figured I will buy one more. As it turned out, I should not have. For one thing, it seemed used (which I noticed only at home), but I really could not see anything obviously wrong with it. However, almost every time I try to shoot with this mag, it falls out, unless I hold it with my left hand from below. Sometimes this happens on the very first shot, sometimes on the second. So far this did not happen with the other 2 magazines (the ones that came with the pistol). Other than that the magazine does not look much different from the other 2. It is not identical -- 15 rd vs 16 rd, small holes indicating presence and number of rounds are located differently and there are fewer of them (only for 5, 10 and 15 rounds) and the D-shaped hole that accepts clip that holds magazine in its position is similar, but not exactly the same (D came from different font?). When inserted magazine clicks and stays where it supposed to stay, no reasonable amount of pull will release it. Cycling the slide with or without rounds also does not release it -- only when actual shot has been fired. Any idea why is it doing it and how to fix it? Thank you.