Sat Nav Erratic Selector Knob

[peterloc]

Has anyone had this problem? When using the lower RH Selector Knob to select any data on the TV Monitor screen ie. Selecting Sat Nav info, or selecting radio channels on the screen, the cursor jumps to random positions and sometimes makes an erratic selection. I suspect there is a poor electrical contact with the rotary selector knob. Its very annoying when trying to put in a new sat nav address as selections are made before i've finished entering data. I have a 1999 BMW 530D Auto. I have removed the control panel and the Control knob is connected to Phillips unit ref:61CY220739926D this unit has plug connections and plastic board connections to main board. I've checked all these and they look clean.

Is it possible to buy a replacement part 61CY220739926D which i susspect is causing the fault.

Tv Monitor on Board Computer is the 4:3 screen BMW REF: 65 52-8 374 914B Phillips Ref: 3112 328 54131

Any help or ideas on this problem would be welcome.
peterloc