In Kaye's radio interview he cites the contradictions which makes it difficult to judge Cooper's performance level and identity. Kaye identifies these as 'A' vs. 'B' and cites specifics: put chute on easily/took defective front pack with him, referred to the chutes in terms no skydiver would use, knew the 727 could be jumped but had trouble with the rear door/stairs, thought the stairs could be lowered automatically from the cockpit, his choice of backpack, assumed the pilots would know and take off and land with stairs down with no objection, etc.
These contradictions may simply indicate that Cooper was "out of date", which could be a product of his age (early 50s) and a person using the past as his reference points.