one of the servos is probably bad. move the servo arms to level, then plug a battery in. if the right servo arm goes down as far as possible and kind of quivers or jitters, the servo is probably ruined. to make sure, take the plugs for the servos out of the reciever and switch them, then test again. if the same servo malfunctions, the servo is ruined. if the other one malfunctions, the reciever is bad. it is probably the servo, though. i had the exact same problem a while ago. the servo had gone bad.