Is it ever possible for a user/patron to change certain data fields that have been incorrectly enter
I am aware that certain fields might allow this depending upon the record source and whenever you see the "Edit" option provided alongside of the data. But I have come across some census records in which the age has been incorrectly indexed vastly differing from what clearly appears on the document. To my knowledge it usually only the names and locations that allowing "editing" of the index data.
I also have a male relative with the given name of Vivian but was incorrectly enumerated as female. Hey, I can't blame the enumerator for that one. 😀