The drive cable is only 2 years old and looks fine, the gear box was completely overhauled when I did a complete mechanical rebuild 2013 and has only 10k miles on it. The trip reset pin has broken and the boot has cracked, letting moisture into the unit, so I am guessing its either corrosion or part of the pin is jamming the odometer. Since they are not replaceable by BMW and Peter wants £240 for the refurb I'm going to bite the bullet and send it down to him after Easter.