It was the output shaft. It just sheared. I have another one on a flybar'd 450 but once I test that other servo I will probably order a replacement. Just don't trust these anymore. Oh on another note.. when I landed hard one of the other motor mounts had twisted on the boom. I had never installed the grub screw into the motor mount. Maybe that's a good thing? In a crash then the soft metal has less chance of bending?