Hello, I have the same problem. The only interesting thing is that I have this with the two cameras with the black housing. I don't have this problem with the cameras with the white housing. I received and set up all 4 cameras (2 black, 2 white) on the same day. If I place black and white next to each other and start to dim the light, the camera with the white housing simply switches over at some point and the camera with the black housing starts to switch between night and day vision every second and does not switch off. I have now been in direct contact with HUE Philpis for a month. No success. Just phoned Galaxus today. The black cameras are now being returned. (I can't explain why either. Software was the same everywhere)

Changing every second is certainly not normal unless the lighting conditions change every second.
Clicking is (unfortunately) normal when the lighting conditions change accordingly.

I also have night vision on Auto but you can only hear the clicking when it gets dark or I change the light. I don't think it's normal if it changes every second.

In the video settings, under "Night vision" you only have the options "Auto" & "Off". From what I've seen, you can't always leave night vision switched on. But you can switch on the light with the Hue app ;-)
That's what I do, because otherwise my girlfriend goes crazy because of the clicking noise. I hope they'll fix it with an update. It's a pain.