Poblem with hydra 120

[U.L. HYDRO DRIVER ICE]

Every time I turn the esc on the servo starts glitching and motor runs off and on with out me touching controller . When I unplug servo motor throttle runs fine and I have tried different servos . Im running a 3s lipo 11.1 volts 4000hv and a futaba 2pl am and a 7s feigao motor thanks and appreciate any buddies time

[Steven Vaccaro]

Disconnect the bec by removing the red wire and add a rx battery pack and see if it happens?