Decades ago I had what I called the zipper effect--rapid clicks that reminded me of a zipper opening/closing when using the wheels. I rarely use my CZ, so I don't know if I still have it. However, I seem to remember it might have been tied in with my PC/sound card.
Do you have your CZ connected to a computer? If so, do you get the noise when the PC is not on and the CV is not connected to it? Also, if the CZ is connected to other gear, do you get the sound when the other gear is off and not connected?
Steve