Discussion about the Korg PolySix synthesizer

Completely different idea: Is the knob for the Tune Potentiometer
positioned correctly?
Since the potentiometer shaft is knurled (and not a "D" type shaft) it's
easy to push on the knob one or more "ridges" to the left or right; in this
case the apparent middle position as indicated by the knob would not be the
middle position in reality.
I've come across this occasionally (though not in this scenario).