It seems the pitchbend potentiometer is broken. Because UF keyboards is stopped production many years. So there is no spare parts for it in the factory. Sorry about this.
It seems you don’t need to use pitchbend function now. The fastest way is disconnect the pitchbend line from the circuit board. In that to avoid the useless message for you.
Hope this will help you, If you have any more question, please send mail to me. ([email protected]) Thanks.