Part of the panel is not working? This usually is due to the loss of the conductive film at the diaphragm, or the bias voltage is not present because it is interrupted in a sector. There is a DC bias voltage across the whole panel. Typically this voltage is around 2K V. There could be many reasons why that section of the panel is not polarized with this DC bias voltage, making the sector to be dead.
The conductive coat of the stat panel is made at atomic level. There is an adhesive that was developed by the Kansas University with the aid of the Nasa to make a plastic to be conductive. Martin Logan had its participation with the developed of this adhesive. Sometimes this adhesive fails, and we have a dead sector at the panel. Why this happens is still unknown.
There is a new adhesive coat circa the year 2000 and up, which its made with aluminium, and there is a new thinner diaphragm, weighting less than the air that it moves. This new technology to build the stat panel, did stop the panels failure and making to be very good with the life span.
Here in Costa Rica, we have a very humid and changes dramatically in our weather. Sometimes we have could weather (not as bad as you have) and suddenly we get hot weather. Humidity sometimes is 100%!! This makes to fail a lot the old technology. On these days, I could say that are just a few with a stat panel problem.
All Martin Logan stat panels have a 5 year warranty!. If you have a problem, just contact their service dept and you will get the best service that you can find.