Update List Values Thoroughly
If you replace a value in a List, any records currently using that value are not automatically updated and can no longer be searched for and found with the deleted value. When editing a List value, it is a good idea to first add a new, updated value to the List, then find all the documents with the old value, and (using the Document Viewer, Search Results Grid View, or Update Documents feature) then replace the old value with the new value. Once that is done, return to the Field Catalog and remove the old value from the List.