The figures, for anyone assembling their own picture. One practical note: write down what you did and when, before you need it. Reconstructing a timeline from memory three months later is how people end up unable to answer the one question that would have resolved it.

Worth separating that from storage and cold chain, which this thread keeps folding into the same question. They behave differently and the advice does not transfer.

A narrower follow-up, since the general answer is now clear:

How would you tell the difference between that and the alternative explanation?

Dr.PathRoch said:

One practical note: write down what you did and when, before you need it.

I read this differently from Dr.PathRoch, on substance rather than tone. I think the framing smuggles in the conclusion. Ask it the other way round and the obvious answer reverses, which usually means the question is doing the work.

Dr.PathRoch said:

One practical note: write down what you did and when, before you need it.

Correct, and worth adding that it is reversible. Nothing being described here is a one-way door, which changes how cautious it is reasonable to be.

OP back with an update, since a thread like this is useless without one.

Following this thread I went back and re-read the extension data properly. The point about trough rather than peak explains the pattern I was seeing on day six, which I had been blaming on the vial.