If you are working in a report, and you find that a product is in the wrong “department”. So you go into that products properties and change which department that that product. The question is even if your future reports are correct, will the past reports be correct or will the past always be listed wrong?
Think of the past reports as information snapshots at the time that transaction happened. So wrong ‘departments’ will remain that way. New orders with your product would show the new, correct ‘department’
Maybe save a local version of the report and manually replace the wrong department with the right one if you need to do some analysis.