OOO this is my strong suit!! i have a chestnut ottb w a very very very similar problem that has been resolved by dressage! i was not a fan, my heart was in te jumper ring but i thought i would give it a try! it made her think and focus on me and my cues soon this came into play when jumping ,, i always relay on TONS OF HALF HAULTS. Now we are sweeping it up in the hunter ring as well as jumpers and dressage😊
If you’re relaxed, they’ll relax. I know, easier said than done haha...but your attitude will affect theirs! Maybe put headphones on when you school to get in the zone.