Backup camera at time gives a real grainy black/gray image, and then suddenly at times gives a normal rear view with the colored zones and lines. Thought camera was bad, but been intermittently working. Any suggestions? Loose connection? Should I start in back and remove inside plastic panel to access. Have not torn apart lift gate from inside previously. If bad any discounted options to replace - are there many different models of the 19G490 camera (many look very similar).