Ridiculousness like this is why I’ve stopped coming to these forums for the most part.
OP he could be a very nice little horse, who scooted in a spook when something unexpected startled him. It could also be that the saddle really doesn’t fit, or… it could be he was on some sort of “calming supplement” that is no longer working or… or… lol.
Do you have an experienced trainer that could watch him be longed and worked and offer their opinion on what they see? It really could be that he’s used to a heavier workload, and now with some “free time” he’s er… exploring some interpretive dance options. lol.
Do let us know what the vet says, and if you’re ok sharing his pedigree, I’d love to see it.
He sounds like he could be a good boy, don’t lose heart yet.