Does anybody else want to try modifying their magazine to see if it fixes the mag drop?
I looked at how both mags are held in place in the Shield. My short mag has more engagement with the mag release than does the extended mag. I used the hammer and punch fix on the extended mag and, voila, no more mag drops. I think it is a mag problem, not the gun. S&W could probably cure the mag drop problem by simply(?) changing the extended mag specs.