I guess the first question of how to track this would be what kind of metrics are you seeking to measure so you get the desired data points.
When doing pfm and full cast, if there were an issue requiring recasting, it would be noted on the back of the script. It was not a big lab, but every tech, save the model tech who handled every model and would always do so, would note their involvement at what stage with what material, and weight if metal tech.
The original(s)/failure(s) (some days you just can't win) would be left in the pan in a c&b box with a 'X' on it until the case was packed for shipping or delivery.
For a larger lab where everuthing is not known between the handfull that needed to know, would having the lower paid shipping/packing person at that time acquire the chartable data you seek? Just give the shipping/packing person a blank sheet with columns for tech(s),invoice #, dr, date, tooth#'s, and checkboxes for wrong shade, wrong material, chipped, etc and an 'other' for any non-standard event. The packer doesn't need to knoweverything, but just be able to read the techs notes on the back of the script if you're still paper based. Turn in the sheet at the end of the day with the mismills. Even if it's blank. Proof of nothing is still data.
I know nothing of the fancy case management software, so excuse my ignorance if this is infeasible. Does it not track cases through from entry to completion and wouldn't it have a 'sent back to level-x' function for qc notations if nothing else? Could it generate reports of how many 'sent back to level-milling' events occured during a specifiable time window?
Am I talking through my hat so completely in a milling house with useless old schoool ideas?