I have 2 DSC-5020Ls and both of them make the same clicking noise (the cameras). It really doesn't sound right & since I recently purchased these, I'm wondering if this is a defect requiring a return to Amazon,, uncertain whether your link on the DCS - 9XX applies since it doesn't appear to be the same model camera.
update: the clicking noises also were accompanied by the cameras turning themselves whenever they wanted. I had to unplu and replug each affected camera everytime this happened. been in touch with dlink techs & they had me reset all 3 cameras (they already had the latest firmware updates). the next question on their list was to ensure my firmware was up to date on my arris motorola cable wifi router. I contacted arris motorola & was informed that my cable company does that, not them. however, as I explained my problem he suggested I get in my router panel & under the wifi tab select channel selection from auto to manual & play with the different channels. it was set at (auto) channel 6 & I went to 11, then 10 and went down some more until the problem stopped (now for 3 days keeps fingers crossed).
yes the clicking sound was the camera going from day to nite and vice versa but they were multiple clicks,, sometimes 5 or 10 times,, not right. the clicking has now stopped to the one click now changing over & none of the cameras have turned themselves off. hope this helps.