I don't know. I've always liked this case. He may have failed 1 polygraph, but they all passed them as well. Not that I really believe in lie detectors being perfect.
My big question is what did he have to gain by going through all this. Remember, when he showed back up he was not in good health. He hadn't eaten and was severely dehydrated. Putting my life so closely to death doesn't seem like it's worth it for almost nothing at the time. He definitely didn't know this was going to get as big as it did. People get abducted all the time and don't get this kind of attention.
On top of that (just my personal opinion) he always sounds sincere. At the bottom here
you can listen to all his interviews from the 70's and 80's. He really seems like he means it.
The story is incredible, but it's also not like the movie that they made after it either (Fire in the Sky)
. There are differences.