I figured the problem would be something like this. The takedown pin in the Kel Tec PF-9 is of a similar design and has or had similar problems. Not sure what other models use this, I just own a PF-9. Hopefully S&W gets a 100% reliable fix worked out, and future pistols from all manufacturers use something a little more robust than a flimsy wire in a plastic groove!

Now onto the trigger reset problem........