Have fabrication and quality follow an ordinary identified group, with the person doing correction involved. Record fit-up, location, first released result and any correction and reinspection separately, including who leaves other work to do it.
An observer needs cover as well. Who can actually stay with that group from release through correction, rather than drop in at the end and ask everyone to remember?
Does the group identify the exact fitted fixture arrangement? The repair machining date can differ from the date changed parts went into use. I am untangling that distinction in another set of records.
Has the observation shown the competing work as well as hands-on correction? You may need cover for a station even when the correction itself is brief.
Does the purchase still make sense with that allowance? Useful to settle it before the fixture proposal promises an improvement nobody has demonstrated.