I have a 4 camera nvr. At night, one of the cameras consistently sends a foggy looking image. The available light does not seem that different at night. Cleaning the camera lens makes no difference. Is there a setting that could make the image less foggy?
Can you post an image?
It almost sounds like a light interference issue, or a moisture issue.
If the camera has a moisture issue, then it would need to be replaced under the warranty.