TOS-DATA-001Changed by someone elseSomething with those details already exists
What happened
A field that has to be unique — a SKU, a barcode, an email, a set of dates — already exists on another record.
What to do
Search for the existing record and edit that one, or change the value that clashes.
Quote this code when reporting the problem. It identifies the exact check that failed, which the wording alone does not.