Absolutely correct. It is not especially relevant but the BX series of tractors (at least my
BX2200) has no indicator that the brakes are applied. Neither did my JD4700 nor my MF2660. That is NOT a very common feature. The 2200 brakes are utterly useless anyway so it makes little difference if they are applied or not. According to Tractor Data this 2680 has wet brakes surely better than my 2200. If they stuck and burned themselves up (especially while the dealer is saying he's busy, let's look into it later in the year...) Kubota is clearly responsible. Everybody, including that rep has a boss. Demand to speak with the rep's boss. There was something wrong with the tractor causing brakes to stick, or WHATEVER the brakes did, and it is fairly obvious the fault is neither yours nor the dealer's. Worst case -- read your guarantee very carefully and take them to small claims court.
Brakes are NOT a "wear item" in the reasonable context of the guarantee when the "wear" is not wear but rather damage caused by machine failure.
A couple of subtleties here: that dealer did not break the tractor apart unless/until he knew there was very serious internal damage. At that point he also knew he gave you bad advice suggesting you wait to get it looked at. Another is that regional service reps do not sit behind a desk forever and they do go around among dealers visiting and inspecting problems. I suspect it would make a big difference to be eyeball to eyeball with that rep in the presence of the dealer. Emphasize that you have bought 8 Kubotas, that there won't be any more unless this is resolved properly, etc.
Shame it is not peak "tractor show season." It would be really neat to go to the Kubota tent at the Ohio Farm Science Review or the Pennsylvania Ag Progress days, walk up to the sales reps standing around, ask who is the most senior with the company, and introduce this topic while drawing the maximum crowd of potential customers you possibly can. At least in the Ohio show I have met with the regional service rep for Massey-Ferguson very politely, person to person, in that fashion. I have no doubt you could for Kubota too.