Seems your replacement camera and radio are both creating grid lines. If you replaced it with a after market camera they usually have a extra cable or button that can turn on and off grid lines. also check your radio if you can deactivate it there.
Also newer cars have extra grid that rotates when you turn the steering wheel. New camera might not be compatible
I have the same effect, but I'm happy with it, because the double-set of grid lines are slightly different so I can tell different distances to the rear and the sides depending which grid I use.
But if I ever have time I'll look how to disable the extra grid lines. My camera had only 2 wires coming out, so I think I have to cut a trace on the circuit board but I'm not sure. Based on the cost on ebay, it probably would be cheaper time-wise to just get another camera that has an advertised feature to disable the extra grid lines.