I have a Alpha 21 glider (only 2 servo's) with electro motor speed 600. I used it frequently with my own transmitter on channel 42 (40 Mhz) without problems. I replaced the christal with a channel 51 one in order to fly with my son's transmitter (royal EVO 9). The plane has now disturbances and goes out of control for 3 or even 4 seconds. After an emergency landing, I replaced the christal with another one (also channel 51). This doesn't make any difference.
Any idea ??