Sometimes I get the feeling that people's reasons for rejecting a candidate don't align with the real reason. Could be as simple as "we're already hiring a friend of one of our co-workers", but rather than tell you that, they make up a reason that is (legally) defensible but obviously not correct.

This happens a bit in certain companies where an internal promotion has already been decided on, but for 'fairness', they need to interview external applications just to reject them.