Way,way back,before the mobile was a twinkle in a mechanics eye,there were horses, both square gaiters and pacers who couldn't leave the barrier cleanly.However they were few and far between because the education of the horse included quite intense practice at the barrier.I can remember a horse that Norm Gath (Adelaide) had that would not leave the barrier,full stop.Mobile introduced in Melbourne,horse (name escapes me) goes north and becomes a cups/FFA runner.
So,horses for courses? Maybe.My opinion,for what it's worth, is that barrier practice is a forgotten art and the consequences of bad barrier behaviour are not so tough.
N.Z. has the right idea,break in the score-up,cause interference, and outside of the back row you go.
Another reason for horses breaking,especially square gaiters,is poor shoeing.A good farrier is worth as much as a good vet to a professional stable.
Having said that, the cynic in me asks that when a clean gaited horse inexplicably breaks or gallops at the barrier (or a TB misses the start) is it a result of poor education
or ?????