The one rein stop is my go-to when horses are being naughty... but for whatever reason I must not be employing it correctly with her or something. I don't really like having to yank her head around (it seems to make things escalate even more). In the latest case, our little fiasco began with a bolt. She started cantering and veered off course. I pulled her head around until she started to slow down, at which point I started to release her head -- at which point she promptly bucked me off.
I think that I probably started to release her from the one rein stop too early. Also, she wasn't really yielding her hindquarters. She had her head flexed around, but she was still throwing most of her weight out the outside shoulder.
((And yes, physical pain issues have been ruled out. She had a full check up with the vet three weeks ago, had a massage a bit over a month ago, and her saddle was professionally fitted. Vet, horse masseuse, and saddle fitter all seemed to agree that there's nothing wrong with her physically. It's almost certainly a behavioral thing.))