yme, A couple of things to check.When the machine is running at an idle,does the shoe seem like it wants to dance a jigIJIf so,you need to check both eccentric drives.I have seen where the eccentric keyway will start eating a groove internally and this gets one side out of time with the other.The shoe will literally shake itself apart.Premature bushing failure,front shoe drive hanger cracking,and rod that runs through drive shaft at front breaking are common signs this is the culprut.You will have to remove both eccentrics and check for keyway wear. Good luck, Hyper Harvest II