A horse that changes leads may have a shoulder and or sacroiliac problem. If the sacroiliac is subluxated (stuck in motion) then ur horse will have difficulty on one of his leads as well as throwing his shoulder into the turn.
Chiropractic adjustments to sacroiliac and or shoulder with lower cervical spine will help correct that.
Contact Dr Bruce at 781-337-1180 or email at Indekchiropractic@gmail.com