it might be the way there making them now a days.. ive not bought a new losi for a while! make sure your diffs are adjusted correctly if somthing is slipping. if your cranking the slipepr right up and somthing is slipping its definatly the diffs.
theres holes on the 'topdecks' where you have used little screws to cover, and on the layshaft there is a hole, poke a thin driver in to the hole (ooh'err) and then hold one wheel and try to turn the other. you should not be able to move the wheel easy, tighten it up and check again untill its hard to do it. i use the layshaft on the spur to do with btw..
also have you ran the diffs in? im not sure how experienced you are so excuse me if you know how
grab a wheel and give it about 1/3 - 1/2 throttle for about 5 seconds on each wheel then readajust the diffs. this is the way ive found best to do it. each to there own though mebbeh?