The contact owns a 2021 Kia K5. The contact stated while driving approximately 30-40 MPH, while the transmission was shifting gear, the vehicle started sputtering and jerking. The contact stated that the failure occurred while shifting from 1st gear to 2nd gear, and from 2nd gear to 3rd gear. There were no warning lights illuminated. The vehicle was taken to the dealer who diagnosed the vehicle with an erratic gear shift with a grinding sound coming from the transmission. The vehicle was not repaired. The manufacturer was not informed of the failure. The failure mileage was approximately 98,000.