@Leehro If I were you, I'd try to figure out what's the layout of your car's CAN bus(es). First, the interesting question is whether there is a bus that's shared by anything related to motion and the entertainment stuff. Then, if (a) that bus is exposed in the OBD plug and (b) this sometimes reappears, you can attack a CAN bus sniffer there and see what kind of nonsense happens then (CAN does have a very reasonable notion of priotity, so I'd wager that the nonsense manifests as corrupt messages due to ~electrical interference).
I can't think of any connection that wouldn't be either via CAN or wouldn't be just power between the two, and I'd be _very_ surprised if that was mediated by power, so if it's not that I'd be (even more) surprised.