What Are The Loud Clunks?

I have had 2 Spotlight Cam (Wired) (2nd Gen) for quite a while. They are both plugged in and work well. When they come on at night and record they are silent. However, I have added a Spotlight Cam Plus (Wired) today. That is also pugged in. When it records in the dark a very pronounced click (clunk) can be heard both on the camera outside and on the recording. During the day the click (clunk) can only be heard on the recording not the camera outside. It sounds as if the camera is asleep and motion turns it on and it begins recording. The clicks (clunk) are quite loud. As this click does not happen on the 2 Spotlight Cam Wired (2nd Gen) camears do I have a faulty Spotlight Cam Plus (Wired) or is this expected on the new Spotlight Cam Plus?