There were no "mistakes." Aside from using obviously forged documents to bolster their case, the CBS postmortem investigation of Mapes' and Rather's account made clear that the central tenet of their presentation was a lie, and they knew it was a lie a along.
By way of fake "evidence," misrepresentations, innuendo, and outright lies, they attempted to convince viewers that Bush was determined to evade service in Vietnam. But Mapes already knew that Bush had in fact volunteered for service in Vietnam, and had been turned down by his commanding officers because his flight experience did not include the newest jet aircraft. Mapes knew that before she "discovered" Bill Burkett. She simply did not care what the truth was.
Absolutely correct.
Scott Johnson and John Hinderaker have an excellent piece in The Weekly Standard on this: http://www.weeklystandard.com/articles/rather-shameful_1039561.html?nopager=1
They allowed me a guest post on PowerLine in which I discuss similar and related points. http://www.powerlineblog.com/archives/2015/10/harry-macdougald-truth-and-other-lies-2.php