One Channel of Magnepan Mini Maggie sounds lower than the other

As per the title, the output of one channel of the high frequency panels is much lower that the other. The difference between the two high frequency panels is considerable such that I have to compensate this by using the balance knob in the preamplifier with several clicks! Anyways I would like to know if there is something I can do to fix this unbalance problem with the high frequency problems. Hope someone can point me in the right direction in order to solve this issue.  

Thanks in advance for your help!
R.