Years ago, I made an extract from a document and incorrectly typed the year as 1850. I've repeated that year numerous times. For an upcoming issue of Casefile Clues, I retrieved the original document and in reading it realized that the year of the record was actually 1852. As the document is the first one that places the person in his "new location," the year is crucial.
Because I corrected myself, I have to go back and re-evaluate some conclusions that hinged upon the 1850 year.
It pays to periodically review your own extracts and transcriptions.