Finally a Fix!!!
I have spent the last 3 months or so reading internet forums and watching YouTube videos of the mag drop problem with the .40 S&W Shield, but nothing offered a solution to the problem, with the exception of someone putting nylon tubing into the weapon which somehow manipulated something, but there was no proof it worked. I also have fallen into the category of owners who contacted S&W to try and remedy the problem but was unable to. I finally went to a local gunsmith (Duke at DCF Guns in Castle Rock CO) who was aware of the problem, but had no idea how to fix it. Well after some fiddling around by both him and I, he got a crazy idea. First he said "Get a new mag release part from S&W, if they charge you, I will pay for it." I got on the phone right there at his desk and ordered the part which was free of charge. He then shared his plan. he was going to use the smallest Dremmel bit he had and would remove some of the material from the magazine release in order to allow the release to slide a little bit further into the gun. He removed an extremely small amount of material around the little lip of the magazine release that stops it from sliding completely through the receiver from right to left. It took a few trial and error shots on his range but finally the mag didn't drop. Now, just to be sure, I stayed on his range and went through a little more than 100 rounds as quickly as I could load them up and shoot, and did not have issue. I tried to explain the best I can, and unfortunately I don't have any pictures to show here, but this is the only true fix I've ever witnessed or even heard about. Luckily it was for me.