i have installed this unit into an M18. I am also using a Mars R High spped responce transmitter. The servo shakes, does not centre and will not respond to commands. It seems that after a while of operation the servo does settle down and take commands but it is unreliable. I had also tried a KO Propo Helios, turned off the High speed responce function and this seemed to work OK.

Is this a problem caused by the transmitter being digital and the servo is analague? What settings can I use to over come this?

I am not familiar with that particular radio but if it is like Futaba's high response feature then only digital servos will work with that feature.