Wow, I am sorry to hear that was the outcome.
I am guessing this problem should be covered under your state's lemon law. You may be headed for arbitration should Mazda want to dig in its heals. Clearly, the ability to travel a paved road certified for public use is not outside the normal parameters of operation for a vehicle, so you should have a very good case.
Get your money back. They are stupid businessmen not to simply do this for you and make you go away. You need to climb the ladder to get to the person at Mazda who can write a check.
As for the problem, I am pretty sure there's nothing to be done apart from seriously reprogramming or redesigning the tranny or substituting a new one. My guess is that Mazda has decided that the percentage of people suffering this issue will be very small and not worth the expense of finding a remedy. Sad, but I understand the business logic.
As you know, car manufacturers are legendary for making this type of decision. Having just dumped a 7-series BMW when buying my CX-9, I can tell you that your problem is minor compared to people having to spend thousands on problems known to exist in a "flagship" automobile costing double the CX-9. I know, small consolation to hear you're not alone.
Good luck in your fight.