Editor as Contributor
I've noticed that when scraping from the Library of Congress, and other places too, edited volumes end up with the editors listed as "Contributors" rather than "Editors," something I then have to change manually each time.
Just to clarify. This is sadly not a case of mis recognition of fields, but more a case of ambiguity in MARC records. In most cases editors in the LOC are listed in the 700 field. This field merely signifies Added Entry - Personal Name. Someone listed here could be a contributor in several ways, that is why they are listed as a contributer. It is somewhat amazing that in the 999 fields of MARC there is no field for "editor". MARC was not originally created for this purpose, and given that it works incredibly well.
For the time being it is always a good habit to double check what you have scraped.