extremely strong bolting issue
i ride once a week at a riding school and have done so for about 2 years so have been being put on stronger horses for quite a while. not an issue since none of them are dangerous or frequent in any of their quirks. however, one of my most regular horses has suddenly woken up with a bolting issue these past 2 rides. i have since been told it is because he dislikes the outdoor arena and cantering behind another horse / being left behind even slightly, both of which we've been doing. i wouldnt mind if it wasnt constant. i think these past 2 rides, i've been bolted with at least 6 times. i am only 4'11 and he is a fit unit of a 15.2hh cob that rides like a 16.2hh, so its hard to keep my nerve when he gallops off with me. i have had to do a one rein stop already so i do know how to handle the bolting at basic level, is there even anything more i can do about it apart from sit deep, control my breathing and prepare for the bolt? since he is not my horse, i cant even do extra work with him around it. any tips would be appreciated, thank you!!