Looks OK to me. Post up the data file and you will get more help. CAN Bus uses twisted wires so what happens on one, happens one the other. So PD remains the same across the pair therefore maintaining signal integrity and eliminating noise. Dave Hill I think has put up a good example here.
I can't see the voltage level of the can high in the picture. If it's from 2.5 to 3.5 than it looks okay to me. There is a bit interference, but it should work.
What is the problem with the car?
Did you also checked for overload?
You can also ad a measurement channel (channel a - b).
There should be a square waveform than. That way you can check if the interference is different on the can lines.