If you place the one way gear on a setup board you will find that it is not flat. Its slightly warped in certain areas. None of the spares I bought are tweak free, all have some warping.
Adjusting how tight you screw it in into the holder may help untweak it.
But if the rumors are true, Tamiya will be providing a fix for this soon. I don't think they can afford to ignore it seeing the Evo3's are selling like hotcakes at the moment.
Its also interesting to note that on the Japanese site, Tamiya admit to certain manufacturing defects (ie the gear case) but I cannot find a reference to it on the English site. Apparently the problem with the stripped gears is well known in Japan.
What I would like to know is if the second batch of cars Tamiya are producing will be less problematic.