Is it possible you have a EQ setting doing that? If not, it could be almost anything in the signal path from the DSP to the contacts on the harness. Start with those. Make sure a crimp hasn't come loose. Other than that, do your best to trace out the signal path, measuring the resistances and comparing to the markings on top. and those nearby in the same area. Some times even good ones will read the wrong value because of the effects of being in circuit, but that's about all you can do, short of sending it in to Mark or someone else to fix.

Stu