How later fixes reshape the Mark 13 torpedo's reputation

Were U.S. Bureau of Ordnance staff ever suspected of being enemy agents because the Mark 13 torpedo performed so badly?

No. The failures were treated as incompetence and inadequate testing rather than enemy sabotage. Once properly tested and corrected, the Mark 13 became effective.

The Mark 13 must be judged in the condition in which early crews had to use it, not solely by its mature wartime performance. Proper testing and fixes eventually produced an effective torpedo, but that later success can make the TBD Devastator appear solely responsible for early failures. The aircraft, weapon, and organisation operating them had to function as one system. Judging the aircraft after the torpedo and supporting system were repaired obscures why the original combination handicapped early carrier strikes.