Of the 150 or so nonlocking biners I have in rotation at any given time, over the years I'd say 5-10 of them have failed. All of the failures were with bar-gate biners. The cause of failure being the little tensioned metal flaps departing the device seemingly randomly, leaving only the spring behind, and the gate to open and close willy nilly. See attached pictures, with the green boxes indicating a properly located flap on a functioning biner, and the red boxes showing where the flap is gone and only the spring remains. My question is two-fold: 1) Is it truly random, or do we know why this happens? 2) Has anybody ever had a similar failure with a wire-gate carabiner?