This, and plenty more happens at every Agility competition. I see it more and more now that I have actually decided to pay attention to minor details and stay technical in my training. People are just not one with their dogs a lot of the time!
Some of you may not know or be aware.. but there should be an invisible link between you and your dog - both in training and on course. I like to think of it as my "elastic"... it can stretch - be longer or shorter, but I can always feel when I am "attached" to my dogs.
When turning them on course, I feel like I am catching them right at the eyes, hooking them to the elastic and taking them by their faces, and scooping them in the right direction so that they follow the preset path of my fingers.... When I push them away from me on course, I use my arm to shake off the elastic in a fluid motion, cue at the next turn and re-attach the elastic in the turn to guide them smoothly back to me...... change of arms work in exactly the same way - smooth and fluid - I always tell my students: handle in slow motion, but fast :):)
OK... I know that all of the above sounds like a fantasy movie, but it really works. If your dog is going off course, you are not properly connected. Use your body, use both arms, manage footwork, get into position, accelerate in places, don't get caught waiting around...