Panasonic 14-140mm Question

Waking up this thread again I too have some issues with the sound from my 14-140mm.

A lot of the time you just get a low motor noise which is not picked up by the internal mic. But after a while you start getting what sounds like a high pitch whistling type of noise which changes in frequency. Not that loud but it is picked up on recordings and can still be heard over reasonably loud background noise. This is because it is a high pitched frequency type sound. Adjusting any of the settings on the lens makes no different. At first I though it might occur once the camera has been on for a while- but it can disapper as suddenly as it occurs. So intermittant is the best description. The Panasonic instructions do mention"clicking& buzzing" sounds from the lens. Not sure if this is the buzzing sound and why it should come and go like it does. Any ideas?

bill