Axel, video is is one of the most unforgiving circuits to problems. Did it happen all at once or progressively get worse? Just like computers, perhaps reboot the 8.4 system. If no joy, start at the camera and inspect for damage or bad connectors. Disconnect each one, look for any green or white colors, corrosion. Clean and add dielectric grease to each connector. If this doesn't work, could be camera gone bad.
Hope this helps. Keep us informed what you find.
Cheers, Ron