We'd have no idea why your servos are failing. It's not likely to be the receiver, though. The receiver can handle the voltage quite well...it has its own regulator for its internal circuitry. We'd look to the abilty of your servos to handle the unregulated LiPo voltage. That's the most likely source. Even trying Futaba servos may result in the same thing, unless you're using the HV (High Voltage) servos that are just starting to come out. There is no way the receiver can cause damage to your servos.

You'll need to check with the makers of the servos to see what the difficulty may be. Perhaps sending them to their respective service centers would be a first step.