Modern ESCs some times have some wicked noise associated with them.
Even some new digital servos are noisy.

You can try:
Capacitors on the receiver.
Ferrite choke dough nuts on the ESC & Servo wires. (pulled from old PC Motherboards)
Route every receiver related wire away from the motor & ESC.

Quite frankly I fought similar demons about 3 years ago,
I jumped to Airtronics FHSS-2 & never looked back.

Airtronics, Futaba & KoPopro all make some great stuff.