been here a long time ago….
if it's driven the same way as the mini facelift, (and i believe it is ) then it's a component failure in instrument cluster….. i forget what precisely….. (it was some years ago) think offhand it's basically a signal amplifier to drive the needles… takes incoming sensor feed and ramps it up and smooths it out, . i found it impossible to find enough spec on it to make an informed replacement choice, so , only practical solution was to replace the cluster….. either a used one (which screws with your mileage evidence ) OR, which might still be possible, do it properly , with a new one, ask your dealers…. and they weren't that eye watering , i think offhand they were about £150 …..
note that not "ANY" cluster will do, it needs to be from the right model/engine as the speedos are different….
(the ticking needle is a give away….. its the sensor feed breaking through and triggering the needle… )