I dunno.

In a previous life I was a Mech.Eng. in an auto factory. There was a problem that came up on the track with a part in the engine bay failing to seat properly because it was fouling on a small lug on the bracket that held it. This only affected a small percentage of the vehicles of thatt type because the lug in question was most often on the other side of the bracket and so didn't interfere. The re-work required was minimal as the lug was only a few millimeters high and was easily filed away--though it did require the paint to be touched up.

As an apprentice, I got to follow the process of tracking down the cause of the problem and its rectification.

The first solution was to have the guy who fitted the brackets, check and reject those where the lug was on the wrong side.

The second solution was to have the guys who loaded the bare metal brackets into the dip painter check and file the errant lugs off before they were dipped.

The third solution tracked it back to the place were the individual parts of the bracket were spot-welded together. Here they discovered the reason for the problem. The gig that was used to hold the pieces whilst they were spot-welded was worn, which meant that the lug that was intended to ensure that the piece it was on would only fit into the jig one way around was no longer effective for that purpose.

The discussion on what to do about this ranged from: