I think that all to often when we are starting young horses, the mistake is made of being to soft. I am not advocating knocking a horse around but, when leaning over them slap them on the sides, ditto when you first get on them.
I think that with this horse, the owner being nervous/unsure, is the main contributing factor.
I have had several horse that acted out of character with a different rider. One, a. Rey intelligent sharp 3 year old TB, would put in the odd buck or three, to see what would happen. They were never to drop me but just a 'whoopee' I am loving this. When he was ridden for the first time by a very experienced lad, he dropped him three times leaving the stables.
Another lovely young horse was broken by his owner. He was a big horse and she quite short. She entered the horse in a show and, because he was rarely ridden with other horses, he was a bit wary but didn't put a foot wrong - until the judge came to rode him!
The man was a good 6 feet in height and when he put his long legs on the horse, it freaked because it had never had legs down that far!
He was, quite rightly unplaced although he was the best horse in the arena.
I offered to ride him in the warm up area. As it was lunch break there were no other horses being ridden in there so, being the nice kind person I am, I nagged the horse. I flapped my long legs against his side, slapped him on the neck, the butt and his sides. His owner came in on her other horse and was riding her all around the youngster. He got very uptight about this but, after a while he accepted it. Well, that was until I was walking him on the right rein and the other horse came cantering towards him.
I knew the rider was going to leg yield to the inside, the horse knew she was going to move to the inside but the youngster didn't! He shot to the right, took off across the arena bucking.
I was laughing until I realised he was locked on to jumping the rails out the arena, luckily I managed to swing him away.
Altogether I rode that horse for about 45 minutes and he never cared about any of the horses that came into the arena.
He entered his next class, behaved impeccably and went beautifully for the judge. He won. This entitled him to enter the Championship. As my friends mare had also qualified, she asked me to ride the youngster.
He won the Championship.
Later I was talking to the judge and he remarked what a lovely horse he was. He then went on to say that he had been watching me work him in the arena and 'break' him in.
I do not sit quietly on a youngster. I swing my arms around, flap my legs, do all things that might happen and they are use to it from the start.