EuroDriverSD

I currently have an Avin backup camera connected to a Kenwood DNX9990HD head unit on my '08 E350. I had it installed by a stereo shop around 3 years ago more or less. Over the past few months I would occasionally get horizontal lines on the screen when the camera activated but as of a couple of weeks ago, the camera display is very dark to the point it's useless to look at it. The image is definitely there, but extremely dark. The display on the head unit is fine on everything else.
Does anyone know if this is likely to be the camera itself or a wiring issue?