Try some round pen work. Really get after him for turning his butt to face you. Make him RUN. Try to get him to turn toward you to change direction, and give him a lot of praise. You can do this by stepping in front of his drive line to slow him down and then sort of 'bowing' and stepping back a few steps. If he tries to change direction again, tag him with the lunge whip. Might work. Don't be mean, but be firm so he knows what you want. Make him go more in the direction he doesn't want to go than in his good direction. Every horse has a good side and a bad side, and you should work his bad side more to sort of even him out.