I believe this exercise is completely pointless, can anyone convince me otherwise?
Simon,
just let me tell you what happened once in a brewery.
We were quite sure that everything was OK and fine with glass and brittles
A colleague of a sister company came for an audit and found out that we still HAD a weak point

At first We said it was IMPOSSIBLE !
Then he stood for a while looking at the output of the pasteurizing unit and noticed a microscopic flow of CO2 bubbles moving upwards from the bottom of the bottles. He filtered those bottles on a Petri dish and to the surprise of all of us there were microscopic glass fragments

.
We did a process review and found out the reason was in the filling machine

.
I won't name this colleague in a Forum, he was Canadian, I hope he's lurking somewhere in SDF, but I will always remember his good job.
Did I convince you mate ?