Multiple failures "out of the blue" during a high-stress situation would seem to definitely point to poor grip discipline (limp wristing or similar). Glocks are not the only semiauto THAT could happen with. Trusty revolvers, still being a mechanical device, are not immune to failure either....ever lost a cylinder latch or had a cylinder lock up...nothing is 100%. For everybody that has had a failure, there is always that guy who has fired 100,000 rounds with no issues.