The 328' is from the switch to the camera, and in reality longer runs will work to varying degrees. When I'm stumped like that it's time to bring the camera in and start isolating the problem with a short patch cable. Or, sub a different camera at the far end of the long cable. You need to have good test equipment that most of us don't have, or be able to swap components with spares. Otherwise you're just shooting in the dark.