ahhhh
let me explain this to you.
the guy you are dogfighting was at low speed was going toward the your teammate and was really slow.
you were doing the same. being similar in slowness and direction.
he flips all of a sudden and changes direction and speed.(technically speed has direction in it but what whatever). you on the other hand at that moment were still following that direction.
funny part is that he fired at the moment he flipped direction so missile followed you at the moment of launch instead of him. ( or at least was not following anything but then switched to you).