I have shot more than 10,000 rounds through my 627PC without a single issue.You may be encountering a loosening of the cylinder from the rachet. It was a common occurance with the early S&W magnums with right hand threads - less so with the newer models and left hand threads. You have to recognize the symptoms early on and tighten the cyklinder before it totally locks up. When it does you have to gently get the cylinder stop to drop and then turn the cylinder to tighten.