Decreased Camera Sensitivity

[rdflores]

Does any know of a reason that camera sensitivity would degrade over time? I added a 3rd camera recently and the point of view crosses a second camera. Both point to an alley way with one pointing east and one pointing west. If a car is coming from the direction of the new camera (points west), the second camera no longer picks it up. But if a car approaches from the direction of the older camera (points east), both cameras will pick up the car. I thought maybe the front to the camera on the older unit was dirty being that it is out doors and Ive cleaned it, but it still occures. Both cameras are set to the same sensitivity. 

Any comments are greatly appreaciated. Thanks in advance, Rob.

[jguerdat]

Swap cameras to see if the issue remains with the camera.  I suppose weak batteries could be a problem but I haven't noticed that.