Cheesy mag-catch spring in my spiffy new Five-seveN was pulled loose by a bullet tip sticking out of a mag I chambered. The instant I ejected the mag, the catch and spring fell out with it, and could not be reinstalled without tools. The only way the gun could be fired was by holding the heel of the mag in by hand. To its credit, the gun still cycled flawlessly when the mag was held in with my pinky curled under the grip (just lame to shoot that way
FNH more than made me whole with a much better-designed replacement spring (for free) that was impervious to the same kind of issue. Moreover, they sent a spare mag release (even though that part was not the problem). Both within about 7 days of my contacting them.