Hi there,
As this is an analaogue machine, it shouldn't be all that difficult to find
the pots that are responsible for the mastetuning of individual VCOs. Do you
have a diagram and a bit know-how on electronics? Than you'll be able to fix
this in a jiff. You could either use oscilloscope or a simple frequency
counter prior to your ears to get the tuning at the desired pitch.
Good luck,
RVe