I have been there, done enough… not all of course, with many walks of horses and especially experienced with starting/restarting youngsters and problem horses yet this one has me stumped… The most tricky part, the behaviour seems to run in the sire line.
I know the owner of the stallion who is by Art Deco and he is known for doing these exact same things.
This mare, not owned by me, but a family member, is lovely, nicely put together, lunges well, handles well etc but she can be a total cracker to ride. You have to be soft, soft, as in don’t move just think or else she will become a little bronc with cow kicks and wild twists and leaps.
My brain of course automatically goes to look at the body, tack fit, strength or lamness issues when I cannot figure something out, yet this one has been vetted, now multiple times over two years with nothing triggering to be seen other than mild stiffness here and there. (Five year old). Mare gets chiro and massage therapy…
I rode her again today, the owner is fed up, the ONLY thing that seems to make her forget about being naughty is giving her something to anticipate. Simple things, as in, in this corner we walk on a long rein with lots of praise and good girls.
I have chatted back and forth with the owner of her sire and she states this is the exact behaviour her sire does and ultimately why she ended up with him because he is just too difficult for previous owners.
NOTE: This mare was never with the current stallion owner, so not a person learned issue.
I have spoken to a few random Art Deco line owners and they seem to express that their horses were difficult, one person types until middle age teens.
Is this actually something? A sire line that produces unruly but talented babies?