1. Temporary Fix.

Cycle servo plug affected by inserting and withdrawing the servo plug several times.

2. Permanent Fix.

Re crimp the servo plug connector, or replace the servo.

Depending on the amount of gold used in the manufacture of servo pins and sockets, the servo connectors have a limited number of insertions and withdrawals that may be made before the gold plating wears away. As soon as the gold plating is worn in this way, the plug/socket combination is open to oxidation, a natural atmospheric process. When oxidation is bad enough the plug/socket combo will start to go open circuit and this will cause control surface jitter on the channel affected.

New crimps ensure a good level of gold in the new connection, thus preventing re-oxidation.

1. Confirm which potentiometer is affected by substitution and clean/replace as needed. Technical skills needed.

2. Return radio for servicing.

7a. Radiated electro magnetic noise from one or more servos affecting the control movements of other servos in the aircraft. 

Credit for the info. to:

M. Coles SCRCS.

1. Replace the affected servos.

2. Fit ferrite cores on the noisy servos. See the following video link to see how this is done:

Link to video showing the fitting of a ferrite core to a servo lead to reduce electromagnetic noise.

Electromagnetic Noise Immunity. 

1. Rx sensitivity to radiation of electromagnetic noise can vary between different manufacturers.

2. Radiation of electromagnetic noise by servos can also vary with servo design, digitals often having higher levels.

3. Built in noise suppression, (line capacitors), in Rx servo designs can also fail over time leading to lost noise immunity and consequent control surface jitter.

4. Mixing digital and analogue servos  in an aircraft installation because of their differences can also lead to the onset of jitter

If any of the above factors become excessive, control surface jitter may occur, so interference of this kind can sometimes occur when servo types are mixed.

7b. Radiated electro magnetic noise.

Credit for the info. to:

D. Drummond SCRCS

& T. Doyle SCRCS.

Fit a snubber capacitor into a spare Rx Channel to protect the Rx from the noise.

This is an alternative noise suppression device to the ferrite core idea above. These are a commercially available option from Spektrum, or alternatively can be made up much more cost effectively in the workshop. If making up in the workshop, crimping is recommended given the vibration levels typical in model aircraft. 

See the links below:

Link to Spektrum's commercially available suppression capacitor.

Link to video showing the workshop method.

8. Damaged gears in the servo's gear train.

a.) Replace the damaged gear wheel. Depending on availability of spares and skill sets, this is not always possible.

b.) Replace the servo. Investigate why the damage occurred and correct that too.

If the problem is encountered, do not fly until it is fixed lest the problem worsen and you lose a flying surface while airborne, almost certainly damaging the model.

9. Servo is stalled

1. Control surface binding.

2. Pushrod obstruction.

Correct the build problem as needed.