Is it a dc motor controller system? If so try swapping the motor cables off the contactors around and see if the fault transfers to the other contactor or remains on the same set of contactors. If the fault moves to the other contactors then most likely motor related issue, however if the fault remains on the same contactor then most likely controller or wiring related.
Chattering usually happens when bad connection on most controllers.
This is ONLY to be used to report flooding, spam, advertising and problematic (harassing, abusive or crude) posts.