The RF wheel fell off today. Sounds bad....gopher holes and ruts finally fatigued and snapped the e clip holding the wheel on. Shaft OD .750, groove .619." Will try the harbor freight assortment box.
7-15-21 My take... factory set up has .100" free clearance between e clip and washer stack holding on the wheel. The wheel came off on a left-leaning slope which loaded up ( perhaps hammered) the e clip for one last time, snapping it off.
I added another .050" washer to the stack. Bought H Frt e clip storehouse , $7 local. That puts the unit cost @ 2 cents, or else $2 and up each plus freight on line. Used the 5/8 e clip. Machine has 202 hours.