A digital servo should work with a DX2.0. I suspect the servo is attempting to draw too much power from the BEC function of the ESC, pulling the voltage down too low for the receiver to work correctly.

What ESC and motor do you have?

Try adding a capacitor to the receiver. It will help stabilize the voltage. Commonly called a glitch buster, stutter stopper, etc. A couple of options:

http://www.horizonhobby.com/Products...ProdID=SPM1600

https://www.ssl-stormerhobbies.com/c...=ns&pn=NOV5626