He admitted it's a warranty issue and was told by Legal to stop talking, it's what any competent lawyer will tell a client. You can get them to cover it fully but it will cost more than the parts and they know it.
Well, then, it's time to follow up with more aggressive action, and you may not even required arbitration.
First, try HQ again, via hard copy letters (FedEx or USPS Certified Mail), with copies of your service visit paperwork.
Advise them that you reported a specific problem PRIOR to the expiration of the car's warranty, yet nothing was done by the Orlando SC.
Post-warranty, you're out $3,500, and you expect to be reimbursed, as is required by the Magnuson-Moss Warranty Act:
Magnuson–Moss Warranty Act - Wikipedia
Advise that if you do not receive an affirmative response to your claim by September 1st, you will have no choice but to "pursue other avenues to be reimbursed for this warranty repair, a warranty repair that I was forced to pay out-of-pocket due to the Orlando SC's failure to diagnose the problem."
Not a lawyer, but this sounds like a no-brainer case.
It's worth your time to pursue, and it will hopefully get Tesla to behave better as well.
(Maybe.)
Keep us all posted!