I've always chocked the RF moving backwards to a CGI goof up... which can happen alot on films and TV shows. The graphics artist was probably told that it was to move so that Jango could target Obi Wan with his missile, but then was animated to move in the wrong direction. Guessing that they probably spent a ton of money to animate it already, and it was a realtively short scene, they probably decided to leave it. Only fans such as the members here at TDH would notice or really care.