New Orange rx r615x

Using a new Orange R615x receiver with three new Hobbyking Servos, a 6.0v NiMh battery linked to my Spektrum DX6i transmitter, in a nitro powered plane. Servo work fine for the first 2 to 3 minutes. Then the servo's go nuts, are not controllable and the receiver gets hot. I switch the receiver with a Spektrum unit. Everything works fine.