I have a Trex 600 CF, I have setup all of the avionics correctly and they work properly with just the BEC on. When I Plug in the main battery and engage the motor the elevator servos no longer respond correctly, it's like it goes dead. There is a catch though, sometimes the elevator servo deflects to a full aft or nose up position. I have tried switching the RX from an FM to a PCM and same issue. I fear it's some kind of interference from the motor but if it is I am not sure how I would fix that. Any ideas? Here are my specs.

Align Trex 600CF Combo Version
Futaba GY 401 Gyro
3 Futaba S3151 Digital Servos
1 Futaba S9254 DigitalTail Servo
Mavrikk Carbon-fiber main blades
Mega Power 4400 Mah 18C 6S2P LIPO Battery
Futaba 9Z TX
Futaba FP-R309DPS RX.