I'm a little hesitant to jump in here... but I probably know the Gunther text better than anyone, so here we go...
Other than the parachute color, which is attributed to Clara, the vast majority of the errors in the hijacking narrative are found in the second chapter of the book. Gunther is a journalist and uses in-text citations. Most of chapter two is original research, newspaper articles, interviews with FBI agents, Earl Cossey is cited, Himmelsbach is cited, etc. This pattern continues throughout the book, and there's a fascinating exchange between Gunther and a Seattle Field Office SA (forget the name, I detail this exchange in my book) where they are talking about the contradicting eyewitness reports, specifically regarding what color the tie was. The FBI had the tie, and knew what color it was, so this caught my attention.
For very rational reasons, LE controls the flow of information regarding crimes. They omit information or give misinformation to verify the veracity of a story. The FBI dealt with hundreds of false Cooper confessions by asking "what item of clothing was left on the plane." It shouldn't be controversial to suggest this happened with Gunther.
Now, the danger here is that every contradiction or mistake becomes answered with a 'just so' story from a convenient FBI boogeyman. So, in the end, I accept that eyewitness testimony comes with baggage---contradictions and mistakes---and should be used in conjunction with physical evidence to come up with testable hypotheses. And I believe there's some actual investigating yet to do with Gunther. Pull all the strings, that's what I say.
