I busted a screw in masterlink on a HKK chain in NYC traffic and learned that no matter what kind of masterlink, don't ever use them.
So did it actaully bust/break apart or did it unscrew?
I have had one chain come off in the last 4-5 years and that was my fault. It was the ESH but I was doing about 30 mph down a hill and it came off. No issue, it didn't break, I just got to the bottom of the hill and put it back on but tightened up the tension. I run my chains really loose but this time it was VERY saggy loose.
I trust the screw on type master links but the z510 chain I have on now is pinned. I looked at the masterlink that came with it and said NO WAY!