We have had my gelding for 8 years. His ground manners and under saddle manners are excellent. We moved to a new barn 4 years ago and all of a sudden he had problems being lead back to the barn. It is almost always a problem that is caused by people. I worked with the barn people on how to lead him in and out. No results so I observed, unnoticed, what happened when they brought him in. What was happening was that the barn workers were allowing the gate to bang shut on his hindquarters which caused him to bolt going in or out of the pastures. I shared this with the workers. They really didn’t want to hear about it and would not change their behavior. There were many things being done incompetently at that barn and so we found a new barn and moved two years ago. There has never been a problem since we moved to the new barn. I would suggest that you observe what happens when your horse is being led to the pasture and from the pasture. It may be something as simple as the gate slamming shut on their hindquarters. Hope this helps.