I have 5 M&P handguns. 9fs, .40 pro series 4.25", .45 midsize, 357fs, and .22fs. Out of them all, the 9 is the only one that I've had issues with. I'm a lefty, and when I switched the mag release over, the follower would snag the mag release and hang up. I contacted S&W, and was sent new followers which also snagged causing ftf malfunctions. I ended up having to file off the corner of the follower to give it clearance to pass the mag release and continue above it. When the mag release was in the "right handed" position, it functioned perfect from day one. After all the headache, its now 100% reliable with zero malfunctions since.