My daughters filly, had trouble going to the left. She tied her head around a few times and that seemed to do the trick. But...thinking about it....I think she told me she started using some inside leg too....hummmmm, I'l have to ask.
Becky
It seems to be a play issue, or battle of wills maybe, not training since 90% of the time, he's fine. He's not ever done that to my husband, although hubby doesn't ride him much or often, and only in the round pen. They just tolerate each other.