Hunnam:
Check your electrical cables.  I had "twitchy," motors for a long time.  Ran fine, but when not running code the motors would jerk.  In addition the wireless mouse I use would occasionally not pickup all the moves.  Never could figure it out.  One day I was rearranging things on my bench and noticed a big difference in the mouse response.  My supply cords are long I had coiled them to prevent dangling.  When I moved the coiled electrical supply cords away from the wires running to my motors the twitching stopped. 
Bob @ BobsShop - If a problem seems like it could be caused by some sort of electrical function - it usually is.