On mine, it is the rear arm rest that is bangging against the metal shield that it was leaning against when it is folded back into the rear seatback (I don't have the ski passthrough). Maybe that's also your problem. A quick way to test it is to just unfold it out of the seatback and see if the noise is still there. Now, All I need is a way to tighten that mechanism so there's less "play" on it (any suggestions are greatly appreciated). But for the moment, having the armrest unfolded out solved the problem.