Very odd - I had to shim both the front and rear. Bad batch? Who knows.
Could be. I know mine were covered in machining oil, and it was pretty fresh so maybe I got from a newer batch that fixed some old issues? Hard to say really. I feel like a lot of these companies are like that. I know for my Slash I had to return various STRC parts because they didnt fit, I know some people have issues with Hot Racing diffs but mine was flawless. I guess its just not feasible for these companies to do QC on these types of things in an actual rig. Then again I guess that test rig would end up wearing down and producing parts that were out of true.