All electrostatics are susceptible to channel imbalance, and if the culprit is a parasitic charge (rather than diaphragm damage and/or dust), the inconvenient remedy is to play them for days/weeks, futz around with the pins to taste, or stow them away for weeks/months until it goes away.
With persistence you can restore the balance on some of the oldest Stax if the drivers are OK.
Too much FUD in this area IMHO. In most cases only the people who have problems would be very vocal about them (however few), yet I haven't heard of a straight-up failure in years. DavidMahler's R10 was the most recent one I'm aware of.
Edited by 3X0 - 2/7/14 at 5:54pm