Dr.CardioMD said:

The useful move here is to separate what is established from what is widely repeated.

Adding the part of the answer the thread has not reached. Take it one variable at a time. Almost every unanswerable question in these threads is unanswerable because three things changed in the same fortnight, and no amount of subsequent argument can untangle them after the fact.

Adding the numbers, since they settle part of this. Practical: whatever you change, write down the date and the reason. In three months the reason is what you will have forgotten, and the reason is what makes the record worth having.

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

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

DataDave said:

Practical: whatever you change, write down the date and the reason.

Filing a mild objection. Mild because I might be wrong; an objection because nobody has addressed the case that does not fit. The objection nobody has made: this only works if the measurement is doing what we assume it is doing, and that assumption has not been tested here.

DataDave said:

Practical: whatever you change, write down the date and the reason.

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.