I have a 6 year old paint draft cross. He had colic surgery 18 months ago shortly after we got him. He ended up having 15 pounds if gravel in his gut. He fully recovered from this. Last year my daughter showed him at several mini events and combined training shows. He was awesome! He jumped anything you put in front of him, and moved soundly. He has always been a great horse with a great attitude about working. Always willing to do whatever is asked of him. Then, about 30 days ago, a little girl was riding him in a beginner flat lesson. Without warning, he very slowly dropped his head and went to the ground. He has continued to do this under saddle, bareback, and while lunging. I want to be very clear, there is NO malicious intent in what he does. It is very slow and very calm, he drops his head, goes to the ground WAITS for the rider to get off, then rolls. If you can keep his head up, he doesn't drop to the ground, but he moves very stiffly, with his head up high and straight, and his tail is partially erect and continuously swatting as if flies were attacking him. The vet watched him and doesn't feel it's behavior either. She thought possible EPM, he did a round of antibiotic, tested normal, but no change. I don't know what to do next and don't want to give up because he is such a wonderful horse. He is like a puppy dog, coming when his name is called and always being very good with people, he has a fantastic personality! I am at a loss! Any help would be greatly appreciated!