Yes, on a lot of issues Bill Mitchell's characterizations of DB Cooper do not comport with other witnesses, especially Tina's, such as the hair and DBC's general appearance. More troubling, Bill refuses to discuss these differences, or explain them more fully.
Basically, Bill tells his story, and then goes home. He clammed up on me, and his conversations with the WSHM staff seemed one-sided. The only one that Bill exchanges any back and forth seems to be Tom Colbert, although Galen reports that he had a couple of beers with Bill over a period of two hours about 7-8 years ago. I suspect Tom pays Bill, so I am assuming that is why Bill stays in the room.