Wow.. replacing that shaft must have cost a couple of $$, plus taking everything loose to replace the shaft.

I must be a tight @$$,,   I would have got a welder in there welded up the groove-ground the shaft back down square threw on some paint.

Guess the "U-clamp" idea is ok,, it's fast/easy to put on,, but couple pieces of iron with 3/8's bolts would be lots less likey to ever work themselves 'loose'..