Intermittent error 17.

I have a Valleylab Force FX C with error code 17. The code indicates that voltage has been detected without activation. I have managed to duplicate the code three times, but in no particular way. It occurred during output testing, again with the unit sitting idle for 10-15 minutes, and again when moving the unit and it got bumped slightly. I am leaning towards a faulty control board, but I believe it could also be the stepper relays. Any input would be helpful!