3de54455f6 removed redundant base-mapped fields when a valid-for-type field was also set, but that still left duplicate fields in Extra when a valid field wasn't set. This will happen until translators (most notably Embedded Metadata) are fixed to stop setting redundant fields. https://forums.zotero.org/discussion/81262/translator-error-sage-lots-of-extra-data-in-extra
3de54455f6