Just one thought on the herd bound issue. Schooling is different than competition in one major area no one has mentioned yet. Usually you leave the trailer area and take a nice long hack to cross country. There are less horses around due to how much farther apart times are and (unlike dressage) you don’t have multple rings so multiple horses going at close to the same time. In other words, it is much more CLEARLY leaving the herd.
Some horses are herd bound, some alphas may get concerned about the safety of the other horses. Some horses just don’t wanna do it. One mare I rode just projected a lack of desire the farther we got from the trailers and proceeded to refuse every jump in new and exciting ways. I did get her about halfway around the course (schooling show) before I was asked to leave ( so embarrassing).
She had gone schooling without issue, popped over to dresssage and show jumping without issue (at 2 shows - but I fell off stadium at one and forget why I didn’t go cross country…there was a reason). After that, I ended up not showing her again - there were others to ride and that was not fun. I did not own this one.
So yeah, consider the hack from the trailers and everything - that may be a factor and may be something to work on.
