Sorry that I misunderstood your situation, thought you were trying to repair yourself.I can see your concern. Unless you can be there at the dealer cutting grass around the dealership, I doubt they will find the problem. The technician is probably letting it run workout loading the engine with the deck cutting and the wheel motors not being used. If there is a heat sensitive problem, just don’t see a correction unless they get lucky. Any way you could start discussing a resolution involving a generous trade in on another unit? Lemon law in your state? Hope the Exmark tech representative is being kept in the loop. The one sentence in the post above you stated that the engine just stopped, that’s something to share with the mechanic as it sounds like the safety circuit is shutting the engine off, like turning the key off? Could be a bad switch, pinched or chaffed wire or a module if it has one. Wish you luck, hope they can figure it out.