try putting the servo you're having the problem with on another channel so you can tell whether the problem is with the receiver or the servo, also put a different servo in the channel you are having problems with and see what happens.

Where do you fly at? I live about 15-20 minutes from Bradford and i can't think of any fields to fly at in that area. There's a good chance that in the next year or two that i'll have to find a new field since houses are being built across the street at my field.