I would take them apart and reseat all the cables, especially the flat clear plastic printed circuit cables if there are any. Be careful to understand the cable locking mechanism and make sure to unlock the flat cable before removing it. It should pull out easily.
You might also play with some settings, does it do it through the DVR as well as direct (i.e. AV1 vs. AV2)?
Try different resolution settings like PAL vs. NTSC and SD vs. HD and 4x3 vs. widescreen.
If it has any video out or video in connectors, try those. I would guess that video out (from receiver) would be OK, but video in (to display) would show the issue.