Broncing issue

[KarenAlbie]

Hello I’m new to this whole this so please be kind ??
I bought a welsh b last year as a 3yrl and he came with a lot of issues and an very small saddle, now I turned him away for a good few months and brought him back as a 5yrl this month to do some light hacking, today I went for a canter and he put on the breaks and bronced he managed to get me off three times on the grass so I need a bit of help
I’ve had his teeth done a new saddle fitted and the physio out and also been lunging him daily, with me getting on and walking and trotting he’s got nice muscles and a nice top line so I’m unsure of what it could be

 

[millitiger]

Have you tried a different/Pro rider on him?
Is it your first canter on him?
Has he cantered before under saddle?
We're you alone or in company?

So many questions sorry, it's probably something a pro can work through and nip in the bud quickly as really depends why he is doing it, which is easier to feel than work out over the Internet ?