I've just looked at mine as it's sat here next to me (not even used!).
Mine has the same slop, it appears that it's coming from the hub sitting on the outer hingepin, if you press the hub forwards of backwards towards the arm, it does remove some of the slop. So there's one way of getting rid of a bit of slop, add some thin shims or ditch the plastic shims for something ever so slightly thicker.
There is still some slop on the axle though, this could be the bearings or the axle though and it is minimal!
Even with that slop, it's not a major issue, I run the Losi 8IGHT and anyone who owns one can tell you how much slop they have, it still performs well though and I don't think that the durability or wear of the parts is affected by slop.
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