Original sentence: However, a clerical error had sent many of the documents to the wrong office, so when CIA workers were destroying the files, some of them remained, and were later released under a Freedom of Information Act request by investigative journalist John Marks
Edited sentence: Fortunately, a clerical error had sent many of the documents to the wrong office, so when CIA workers were destroying the files, some of them remained, and were later released under a Freedom of Information Act request by investigative journalist John Marks