Every single servo I broke on the throttle in my 1st run kit has perfect gears. Even the lowly P.O.S. standard plastic-geared airplane servo I had to use because there weren't any good ones available. We never quite nailed down what was happening, but for whatever reason, I got it right about 7 months ago. It was the same JR Z590 type servo, several times(excluding the standard, which also happend to be JR). In fact, I gave one I broke to a friend who had another with stripped gears, but the rest was still good. He combined them, and that's the servo on his throttle now, about 4 months old.

That may be what happend to yours, but several of us had the same mystery failure. The servo would just quit, for seemingly no reason. One guy had a servo die, IDLING ON THE STARTER BOX. How did it flex there? My point is we never really figured out what specific aspect of the 8ight killed it. I did however, help to develope steps to stop it through trial and error (took 5 or 6 tries). Even with all the steps that kept mine working, some kits & RTRs still kill them here and there. For the most part, if you use a decent servo and set it up conservatively, it'll perform very well and live a good life span. Mine, which is raced regularly, is testament.