I'm impressed but not too surprised how well the Gibbs did on that test. I'd love to see a more detailed head-to-head comparison of midline attachable devices verses prusiks, etc. August has a pull tester, wish he had time to make those types of videos.
As far as biner gates failing, it's happened to me once or twice maybe? I imagine its something you'd notice at that moment you go to close it, but hardware failures like this are why I blow off and check the action on my connectors at the end of the day before putting things back in the truck.
