I have a brand new 2021 Enclave Essence. Transmission started slipping at 400 miles around 25-30 mph. Engine revs to 4000 rpm before it finally finds a gear. Dealer looked at it once stating they were unable to duplicate the problem. Vehicle shows no trouble codes. Its a very random problem. Dealer wants me to leave it with them for 4-6 weeks as that is the earliest they can schedule it for service. Really hate to pay for a car that is not sitting in my driveway.