losi 8ight 2.0T servo problem

Hello!

I installed new mamba monster system on my truggy.
I have new SAVOX servo: SC-1256TG.
And I use Spektrum DX3.0 Tx with SR3000 Rx.
I can control the forward/reverse well, but when I touch the steering wheel left or right – the motor stops and the servo does not work as well.
Without touching the gas trigger: when I steer left or right, the servo moves a little bit, and then stops. The green light in the receiver turns off, and the motor starts to works alternately.
What should i do? what is the problem here?
Thanks alot guys.

Idan