going from memory, Marks Dock's are wired the same as the Car Sleds (in requards to audio output) so it seems strange that it works in the car and not in the Dock.

This is not strange at all. Let me splain.

The home outputs are physically tied to one pair of the car outputs. I don't recall if it's the front or the rear, I think it's the front. Let's assume for the sake of this discussion that it's the front.

So if Mark's docks were wired to the front car outputs, then failed home outputs would also fail on Mark's dock. And if Boxer's car were wired to only the rear outputs, then his car would continue to work fine.

See?