Don't take "No" for an answer. Call customer service, explain your experience and how potentially dangerous your safety is, and tell them that they need to look at your Shield again. When you send it in, include in the box a note saying that your Shield will fire with the safety in a "middle position" that it's not supposed to have. My experience wirh S&W customer service has been very positive, so give them another chance to make it right.
I'm the same way. I'm just getting my ducks in a row. And to your point about letting them know it will fire in the middle position, I actually made almost that exact statement in the note I wrote that accompanied the firearm.
I've sent M&P's in for service on three other occasions over the last 14 years I've owned M&P's (four all together), and each time it has take almost exactly two weeks (and never more). This is the first time it's taken three, so maybe they are just busy at the moment and simply overlooked this.
I also agree with you as my experience has been mostly positive with their customer service, but I do have three or four exceptions to date. Two are from this experience (the trigger doesn't seem to be appreciably any better than my last non-PC Shield and—of course—the problem with the manual safety).
The other problem I had quite a few years ago was with a striker that broke on a new M&P Bodyguard 380 the first day I owned it (when they originally added the M&P facelift). I wasn't upset the first time it happened (these things happen), but I WAS annoyed that the firing pin broke a second time a year later).
The third issue was a brand new M&P9 M1.0 I owned right before the M2.0 line launched. Someone had clearly damaged the channel for the frame tool. I don't know if it was someone involved in the manufacturing process or someone working at the store I bought it from new, but someone jammed the tool in there so much that they not only broke the notch on the tool itself, but they deformed the channel the tool went into (so that it was oval and chewed up instead of round. As such, it 1) looked unsightly (not that it would be noticable when the tool was in place), and 2) it felt different from my other M&P pistols when I rotated the tool in and out of it. I had asked for a new frame in the letter I enclosed but Smith & Wesson just returned the original deformed one without comment (other than noting they gave me a new frame tool).
This was one of the last M&P M1.0 versions that they made (with all the updates, and it happened to have trigger every bit as good as my two M2.0's in my opinion), and all this happened some was some 10 or 12 years or more after owning my first M&P pistols, so it's not like I didn't know my way around them. When I ran a business, I would from time to time eat the cost of something even more expensive than a M&P frame to make my customers happy, so although I didn't care enough to pursue it beyond a complaint to S&W—and although I do feel Smith & Wesson's customer service is better than most—I no longer consider it exemplary. I didn't demand a new frame because I was sure that the cosmetic damage wasn't
likely going to turn into a problem (e.g. the tool not seated sufficiently at some point), and given they have a lifetime warranty, it wasn't going to be a problem for me (though it might have become one for the next customer), but I also believe in being forthright with customers, and if I didn't call someone myself, I would certainly have one of my employees do it just as a courtesy and to ensure the customer agreed and was satisfied. Smith & Wesson, however, didn't even dignify my request for a new pistol with any response—at all. Similarly, they didn't acknowledge anything this time about the trigger or the manual safety.