i tried that too short shanked didnt help, thanks though!!!!

We had a horse that did this too, we used hack on him that is just a leather piece and flat with long shanks, it worked really slick. I think we still have it and I can probably get you a picture of it. This was was extremly broke though and had a good whoa, maybe you need to put some of that back in him as well? Hope this helps?

Sounds like it's not in his mouth, so I don't think it has to do with what type of bit u use. U say he does it when YOU ask him to side pass or stop. Does he do this on HIS own when he is in a round pen(stopping)? try checking his physical condition out. Out in the poll, sore hocks, or in pelvic - stifle area. Some of it may be habit, but not all of it. I definitly would have a GOOD chiropractor check him out.

Does he do it in both directions are just going one way.? He may like was said be out some where.Watch a horse move loose in the pen and just watch.If they are soar they will move in one direction more than others.Also you might put him in a place like a lane and make him move around not stepping in front just drive him up into a corner and have some one shoo him back to you just force him to turn and watch what he does with no one on him.If he doesnt want to and goes one way more than the other on his on he is soar might be in his neck or shoulder We had one that was out in his knees and he wouldnt turn right.Your saddle could be putting pressure on that side also they will not want to turn into it.
Which way is worse or only is it one way?Thats a thought Its awfull hard to say when you cant see the horse.

thanks that is good advice I am on the search for a chiro in our area!

I ran into this same problem with a mare that I have. What I did was went with a chain bit with a very long purchase and took off the chin strap. She works like a champ now! Also I know you said you had her teeth done but have you checked for wolf teeth? These can be a huge problem especially in mares? Hope this helps. Also try a tiedown with a rope noseband and see if getting her nose sore helps at all?

After all medical has been checked as suggested, look at some of the english hackamores. They make some nice ones. Leather adjustable straps with wool lining. They have excellent contact but will not sore the nose. Some english bits do wonders for a "western" horse.
Hope you find the cause soon.
Kathy