I think you will find that the answer is none of the above. If you pull the top off the servo and look at the gears with a magnifying glass, you'll probably note that the gear mesh has been forced or jammed to one side of the gear due to excessive loading from the servo arm. It will look like one gear is wedging it's teeth a little under the bottom of the teeth on another gear. Time for new gears.

I went through exactly the same thing with some 8611's a short time back and that's what was found by the repair folks. It's caused by having the linkage attach point too far out on a long servo arm when using large travels.