Occasionally during the machining process, a small burr can be left on the gear teeth. Open the case and inspect all the gears and using a small file, remove any possible burrs that may be left. When re-assembling the case, ensure that the gears are well greased.
In most cases, the gears will settle in after a couple runs. If you are still having an issue, please email us at firstname.lastname@example.org as we may need a video or photos of your issue to better troubleshoot.