There is an ILLEGAL way to modify digital odometers but one would need to find a trustworthy source to ask for such a service.
As for the topic at hand, its possible that the method your rollbacker used may have either damaged part of the unit or perhaps this is a failsafe or telltale sign for when the odometerhas been messed with. Im just guessing all of this though. Have you tried to reset the ECU by disconnecting the battery?