Dunlop Straplok Gold Dual Design

I have this type of locks on two other guitars and I've never had any problems, so naturally, I bought and installed Dunlops on my third guitar. On the second rehearsal with these brand new locks on, suddenly one of the locks failed and my guitar fell down. Since then, I'm sceptic... And yes, I've double checked the locks before hanging on the guitar. The lock is based on 4 little bearing balls that fit into a circular groove and lock there while being pushed by a spring and a locking pin out of their holes. Something went wrong there...