Korg Poly800/EX800 Users

I have a MKI Poly800 that is about a half step flat, but its constant, no wavering.  What I found as a work-around is to push the joystick all the way to the right (highest), adjust the tuning slider until its in tune then let go of the joystick.  If I then turn off the power, push the joystick all the way to the right again and turn the power back on the thing is in tune.