They go nuts in less pressure situations? Maybe arena sour?
Or perhaps not accostomed to the real world? There was a very sad situation a few years back where a woman in Nevada was dying and the breeder of her nice dressage mare was trying to place the mare, a National Show Horse. We were looking for a dressage horse for our grandson Gabe and I was looking for an endurance prospect. She sounded like she would fill the bill, so I paid $1000 to have her shipped to Oregon. Now, in defense of the mare, this was a horrific number of changes for her in a very short time and four years later she is doing very nicely as a high school equestrian horse. She NEVER leaves the arena, but she has adapted to pasture turnout. When the shipper arrived at Creekside, he waved a lead rope in my face. Claudette had eaten through it her first ten minutes on the truck. She had always gone from her stall to a dressage court and back to her stall. She was terrified of grass, couldn't drink from a water trough, dropped a ton of weight. She was rideable in the arena, but when Gabe took her out on trail with a group of 4-H girls, she had a terrible wreck. He came off and she cart wheeled down into a ravine. He thought she was dead. After about three months, we decided she just was not safe for either of us. I never even got on her. After Ashley took her over, there were several other horrific wrecks. She came out the front of a horse trailer, or tried to. She bumped the gait to the arena when being led, bolted and fell over a bank and into a creek. The point of this whole story is that it is possible for a horse to be quite good in the familiar and controlled setting of an arena and quite dangerous in the big out-of-doors. Nancy