I have two Futaba S-3303 and two S-134 quarter scale servos. All exhibit the same problems when connected to channel 6 (flap) of my R-148 FM receiver using a 9 inch lead. Each time the servo is moved to a new position, it oscillates about 3 or 4 times before taking up the new position commanded. When connected to channel 1 (Aileron) using a 9 inch lead, operation is perfectly normal. This problem occurs using both my T 8UAF transmitter and also two older Expert transmitters on the same frequency.

I have inspected the feedback pots in all servos and they all appear in excellent condition. I cleaned and lubricated them with pot lub and no improvement was evident.

When tried with two older Expert receivers on the aileron channel, all servos oscillate constantly as soon as the r/x is turned on. This occurs with both the Futaba and Expert t/x's.

It appears that this is a servo/receiver problem. Since both these model servos are no longer listed, I am wondering if they were withdrawn from production due to these problems.

Servos get withdrawn from production because demand had gone below that needed to sustain production, or because better designs are available. Sometimes the servo's withdrawn because it has to be redesigned as a result of a parts maker not making certain parts anymore.

In the case of your servos, the long servo leads could be a contributing factor, or the location of the leads in relation to other leads. There could be a problem in the servo, or a problem in the receiver. Sometimes the signal driver in the receiver is a bit weak, so oscillation can develop if a too-long lead (or sometimes any lead) is attached.

Since the problem happened on different brands of receivers, the problem looks like it's in the servo when it's in a particular configuration.

The servo may need to be looked at or replaced.

This may sound silly, but I've had this happen before. I had aileron servos do this on a 27% Extra model, and on elevators from another model. I've found that the connector that is disconnected (when removing the wing) must be getting dirty. I can engage and disengage the connector several times, and the problem goes away. Check to see if your connector and pins are dirty.

I'm not sure if there's a difference whether gold plated connectors are used, or not - I've seen the effect on both.

What Ron S says
Had the same problem. After replacing servoes etc I finally discovered it
was a bad connection on the extension cable I used. It was brand new but
something about it apparently was not right.