That silly collar with the one screw that holds it in, no bueno. There's an o-ring on that collar, replace it. I made an aluminum plate with a hole drilled where the set screw goes. It holds the collar much more securely, and I haven't broken my subvalves again since doing this mod. I think when that collar gets offset, it can cause the rod to bind up against the subvalves and sheer the teeth off them. At least, that is my explanation for the failure of my first 3 sets of subvalves.