Casio CZ/ VZ/ FZ - Pro Series

Just got a used CZ101.
It's all fine but the bendwheel.

Halfway up and halfway down it stops bending and turns silent (down) or jumps to an 
extremely high frequency (up).

Took out the potentiometer and tested it. It seems fine but it's quite far from its printed value 
of 50k. It's something like 42k.

I guess it could help if I change it to one closer to 50k. Anyone who's tried this?

But I also though maybe there's a way to adjust the bend balance inside the CZ101. I notice 
there are at least four trim pots inside the machine. But I have no idea what they do so i 
don't want to adjust them at this stage.

Is any of these trims involved in adjusting the pitch bend range/balance?