Toraiz AS-1 Background noise problem

Hi,

I have an issue with the Pioneer Toraiz AS 1 synthesizer.
Specifically, I am experiencing background noise, clicks, when changing the parameters of the synthesizer as well as programs.

The noise and clicks are noticeable during three actions:

1. - when I increase the FREQUENCY LFO knob and INITIAL AMT while LFO is assigned to VCA.
2. - when I increase the DEPTH knob of the chorus effect in the FX section.
3. - when I change programs.

I know that the firmware of synthesizer is no longer supported,
but perhaps you have a similar issue and know how to resolve it. It is possible that I have a faulty unit? 
If necessary, I can send sound samples. Thank you very much for your help!