I just bought a dozen servos (I'll leave the brand out of it) and in a trial noticed they emit a high pitched squeal, interrupted but not consistent interruption, and sound a little like morse code.

There is no chatter in the servo itself but if I push against the arm whilst activating it, the squeal gets louder.

These are metal gear servos, and were a good deal so I'm reluctant to either take them back or pitch them. I think they were probably made in China, but aren;t most modeling things these days?

Does anybody have any ideas or advice on these?

I appreciate your help.