Discussion about the Korg PolySix synthesizer

After many years faithful service, my polysix seems to have developed
a tuning problem :-(

Usually when I first switch it on, and initially hit the keys, the
VCOs swirl around in pitch for about a second? (I presume that's some
kind of autotune routine or sthg.)

However, recently, when I turn it on, this doesn't happen, and the
oscillators stay at some kind of wierd tuning (all the notes seem
stretched out, the octaves are about a third or more off pitch!)

One time, I left it for about 20 minutes and when I tried again, it
was back to normal.
But yesterday it just remained in this wierd state.

Any suggestions to make it behave?
I made sure that the pitch bend wheel was centred at power up.
The VCOs are switched to "stretch tuning" inside, but that's never
been a problem before, and this is orders of magnitude more stretched
than that.

It's not a NiCd battery calamity, as my Polysix was upgraded a few
years ago to a "PolysixM" (with lithium battery) (Johannes
Hausensteiner's mod)

DAVID