Brindle Thoroughbred Race

Hi guys and gals, Got a weird problem I need help with. In the race against a woman who is riding a Brindle Thoroughbred just south of Rhodes, two of my well trusted horses go insane. I have no control over them other than speed, and when they get even with the woman/brindle they dive into her path and try to cut her off. If I keep them at full speed they eventually run into a tree and kill either me or my horse, or both. What's going on? Like I mentioned, I've tried this race with two of my well trusted Level 4 bonded horses and both are doing it. Thanks! 🤠