With BMW being so specific on the production #'s I have a feeling they rockwell hardness or material used to make these levers were the problem. If they are soft they will wear faster and increase tolerances. When and if I replace my levers and shafts I will have the Rockwell tested at my job on the old ones and new ones. I can also have mico-grain structure analysis done if I really wanted to put that much effort into it.