Seems to me that I fixed the odometer on my 1977 240D by diddling with
it while watching a one hour TV show.

The gears tend to slide sideways on the shaft and get out of mesh.
Also the shaft is knurled and if a gear starts slipping, it has its
hole enlarged and spins around on the knurling. Both the gear hole and
the shaft knurling wears.

All I did was rough up the shaft knurlings by using a pair of diagonal
pliers then pressed each gear sideways until it was again at its
correct position on the shaft. A drop of Locktite also helps.

As mentioned, one the odometer was disassembled from the instrument
cluster assembly, the whole operation took less than an hour.

Doug