i know this may sound a little silly, but every so often (at least with me anyhow) you can strike a ball and put a three demensional rotation on the ball, manytimes due to the ball having a heavy spot. while having normal back spin, as it slows down some. the ball will turn over, causing a late turn one way or another, or the centralfugal force will turn the ball. iv'e had many range balls go sometimes two different ways while in the air( self correcting).

please don't beat me too much on this one.