Agree with Dombrasky, it's the Savox servo. They are very power-hungry. Despite the use of a 2S set-up they can easily overwhelm a receiver that uses its thin bus bars on the circuit board to try and pass up to 3A. That just sucks the life out of the receiver. A capacitor might help, but I'm not optimistic.
I run my FRSky with a 1S set-up using a Futaba servo. I found that making sure one aerial was vertical, and one horizontal, helps greatly with range and rejecting interference. Also, make sure that the Tx is on HRS setting for both Futaba and FRSky receivers. I found this best for range and response. HTH
