Looks like it cracked on the tip side first, then the rear failed, see #2 photo. you can see where the surfaces worked before failing. Can't tell from the photo's 1,4,5 what or where the shaving? came from.
Not an expert, but isn't the shaft supposed to be installed with the
oil hole down? or maybe they have 2 sets of holes ( top & bottom)
They appear to be of cast material not billet, maybe not the best choice for the application?
Craig