Nearly brushed it off with "it was already wrong before"

Spreadsheets

Situation: After changing some formulas in a shared spreadsheet, a total in another column stopped adding up.
What the AI did: It came close to reporting "this column probably never added up" as an old bug. Checking the version from before the change showed it did add up; the mismatch came from its own edit.
How to ask next time (the operator's example): "Before saying it was like that before, run the same check on the version from before the change and show me the two results side by side."
One question to ask: Is there a result from before the change to compare against?
Check it yourself: Google Sheets, and Excel files on OneDrive, keep version history. Open the version from before the edit, copy the total, and put it next to today's. In code, checking out the previous commit does the same.
AI used (month): Claude Code (2026-09)
Times this mistake was recorded: once
Source: The operator's work records (the details were changed to a different task)