Worth restating a point from upthread for anyone joining at this page:
Start from the measurement rather than the conclusion. Almost every disagreement here turns out to be two people measuring different things and comparing the numbers anyway.
Dr.AddMedPHL said:Start from the measurement rather than the conclusion.
Same pattern here, and in the same order.
Reporting back.
Resolved, and the thing that resolved it was the least interesting suggestion in the thread. Writing that down for the next person who wants the interesting answer.
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Shop Reference StandardsThis was answered several pages up and is worth repeating rather than re-litigating:
Went back through my own correspondence with an earlier supplier and the warning signs were all there in the replies, weeks before the quality changed. I was reading the product and not the behaviour.
A narrower follow-up, since the general answer is now clear:
What did you change at the same time, and can you separate the two now?