I also had a Herm Sprenger Quick Release Prong Collar for my last boy and one day I gave him a correction and it opened up and fell off. He did have a backup collar but it was scary. I returned the collar and bought the regular prong and I've never had a problem with it.I have this prong and it's never opened. Some people feel safer with a backup but after a few years of using it, it's never come apart. Not sure if the different prong styles make the difference.
Herm Sprenger Chrome Prong Collar with Quick Release
I was reading that Leerburg stopped selling the Quick Release Prong Collars because a lot of people had the same problem.