Hi...
Pardon the dumb question: Have you tried hooking these up to a standard RC Receiver/Radio, and see the results?
If they work fine with say some channel on your receiver RC Radio, then you know the issue might be in your sketch/Servo library/PWM pulses coming out...a scope will help you to see those....
If they do not, then the issue is mist likely with the Controllers.....
Just a thought...