DCC throttle malfunctioning

The right throttle knob on my Digitrax DT 400 throttle no longer responds 
properly.  It's most noticible when turning the knob counterclockwise and 
instead of a straight-line sequence the readout might run 
30-29-28-27-26-25-24-36-34-33-32-44-40-39-27-36-35 and so forth.  It also 
happens when increasing speed but not so noticibly.

Is this something that I can reprogram or do I need to send my throttle to

Digitrax for service?

Carter