Never, never use OIL or other cleaning product
I cant remember exactly how to do, but there are a way with a build in "test menu" where you can check many point in the keyboard

Maybe Wittid or other members in here have the procedure
There are a "spring" for the "0" position, but I dont think it is the probs.
First of all, insert the OS again with "INTRO" and after that check the keyboard again (power off and on again). It can also be a bad connector plug or the potentiometer inside with the Pitchbender there have going loose between plastic and Potentiometer (I mean its a tiny screw)
Keep us informed.
Cheers
Kjeld
