Complex sentence: She identified the errors of fact in family testimony which earlier historians failed to note, as well as gaps and errors in the overseer Bacon's account, who was not at Monticello during some of the period on which he commented on events.
Split into simpler sentences: She identified the errors of fact in family testimony which earlier historians failed to note, as well as gaps and errors in the overseer Bacon's account. Bacon was not at Monticello during some of the period for which he commented on events.