Smith & Wesson has issued an advisory regarding the performance of the manual thumb safety on the M&P .380 Shield.
The company says: "The function of the M&P 380 Shield EZ Manual Thumb Safety pistol can be influenced by the type and quality of ammunition used with the pistol. In the case of the M&P 380 Shield EZ Manual Thumb Safety, we have found that in very rare circumstances, ammunition that produces a high level of felt recoil can cause the manual safety to move from the fire to the 'safety on' position during firing. Should this occur, you will not be able to fire the next round unless and until the manual safety is reset to the fire position.