[Overdriven]

I doubt you have to worry about metal shavings. Take the piece of stud out of the adjuster and piece the stud together to check if any chunks are missing though.

Broken rocker stud could be a fluke but I'd want to make sure there aren't any other causes for it. Is the cam really high lift? I'd be checking to make sure none of the valve springs are going into coil bind. Also make sure the rockers aren't hitting the studs when the valves are open. Either of these would put extra force on the stud and could cause it to break.