before explaining why a number moved, how do you rule out that only the measurement moved?

something that's cost me more time than any actual analysis. a number moves, everyone starts building the story for why the business changed, and three days later it turns out a definition or a collection rule moved underneath it and the business did nothing the ones that got me were all boring. a filter changed upstream so the query quietly stopped counting a segment it used to count. tagging or consent coverage dropped so volume fell without demand falling. a platform reclassified what counts as a conversion, same behaviour, different number. a timezone changed and the day boundaries shifted