I've pulled apart a couple of C50 boxes, imagine that you are looking at the hub like a dinner plate. On the C50 boxes there are 3 seperate arms which connect the outer section with the inner spline that slides down over the input shaft.
This is a weakness they seem to have addressed in the later boxes. I swapped in a hub and slider from a w5m33 box both times with no issues whatsoever.
I'll see if I have the old broken bits still.
