Victors & Talons problem; motor jotering PLZ HELP!!

[LATech]

We are using a 4 motor configuration, we have tried both victors (4) and are currently hooked up to talons, in both cases we would try to go forward slowly and the motors would obey, as we tried to increase the speed the motors would start to "jotter"; meaning go forward then quickly go back then forward again. At first we thought it was the victors, which we replaced with talons (which we calibrated) and got the same result. We also switched out the PWM cables with no success, so we don't think it is faulty cables. Please help us as we cannot diagnose the problem.

One possibility is that we accidentally sparked a PWM cable (connected to the digital sidecar) onto the aluminium chassis with everything in it. The battery was connected but switched off (yet there was still a spark. We assume residual power was present and that a negative was touching the chasis).....We don't believe any damage was done to the C-RIO because it still works but we are not sure if the digital sidecar took any damage. If the digital sidecar is damaged then would it be causing this jotter of our motors?