screen jump / dvd through sat nav?

[fosta11]

Hi Al got my x5 4.6 is just under a month ago. I have fitted 2 dvd players with screens to the headrest but when i connect the video output to the female jack av in by the rear seat console and select av on the front screen the picture just scrolls really badly?? the sound comes out ok (although a samll his is audible) Any guesses?
it's a 2003 model with the large screen.