Do we truly know what the problem is? Is it a situation of a bolt that is failing because the forces on it exceed its design load or a quality control issue with the manufacture of the bolt? These questions need to be answered before the correct solution can be applied.
Well I don't believe we are clever enough and I doubt many HD dealers or HD themselves are interested enough. With limited knowledge it is likely one of two reasons, either the metal has flaws in it or the torque that they are using is too great and is damaging the bolt