I have an OTTB which I ride dressage. He has been doing very well. However, recently he has been giving me trouble when I que him to canter from the trot. He will trot, trot, trot, trot, and the finally canter. He is extremely sensitive and I am not sure how to approach correcting this issue. He never does this when my trainer is riding; just lucky me! Any advice is appreciated. Thanks!