I lease a four year old QH gelding at our local barn. He is a very kind horse but has developed some bad habits due to his owner. When riding, he chooses random times to come off the rail (wall) and turn into the center, occasionally picking up speed. He cannot do circles on the right rein due to lack of muscle on one side. His owner works him only on one side during lunging and riding. He can only lunge in one direction, in the other direction, he behaves poorly (taking off, bucking, and trying to change direction, even though we use a lunging cavison).
How should I go about training him, that he should listen to me and forget the things that she has taught him? Will my training have any effect on him, or with his owner also riding him (poorly) confuse him, and cause him to continue his bad behavior?
Thanks for your help