Stock horse gelding 15.1hh 5yrs

Max is a 5 year old gelding stock horse 15.1hh. He isn’t registered. My 13 year old daughter was riding him for 6 months after we bought him and loved him. She took him on many trail rides in the bush and started to teach him to jump up to 60cm. He is quiet on the ground, easy to catch, easy to float and was enjoyable to ride. Unfortunately, just after 6 months he started to rear when she tried to push him to canter or do something he didn’t want to do. We took him to a horse instructor and spent a week with her and during that time he was fine with her. But when we got Max back home he started rearing again for my daughter when she pushed him to canter. We tried some techniques to stop him rearing which the horse instructor used successfully but my daughter just isn’t strong enough to be tough with him. Obviously if you were interested in Max you would need to be an experienced capable rider who is strong enough to be tough with him. Apart from this there are no other vices. My daughter is disappointed to be selling him as this was the only problem.