When the 42" Raptor first came out, missing bolts was one of the main problem as Hustler had only used plain nuts. They finally started using nylon lock nuts.
I only worked on one SD so far It had threw the belt but by the time it got here there was a lot more damage so the root cause wasn't discernible. The customer's wife had dropped a tractor bucket on the mower while attempting to loan it. I had to unload and move it around using a floor jack. Wheels would not turn. Several broken bolts was the result so I straighten out the mounts new 8 grade bolts, changed the belt and and idler pulley. I haven't seen it back yet and that was last year. But idler pulley bearing was shot.