Here's my issue. Maybe someone can explain this better to me. Sorry for being so dense. The cast piece that the passenger arm fits onto is, for the mostpart rectangle shape. The opening in the arm gets wider toward the end with the little catch. Why is it this way ? Why isn't the catch larger so that it fits under the cast piece more? I can fit the arm onto the cast piece, but when i slide the catch over, the whole thing just jumps back up off the cast piece. Mine looks identical to the one pictured above, it just seems like mine is moving on the splines, so i may need a new arm afterall.