The contact owns a 2021 Toyota Highlander. The contact stated while driving at 55 MPH, the drivers side mirror was vibrating abnormally. There were no warning lights illuminated. The vehicle was taken to a dealer and the vehicle was diagnosed and it was determined that the screw securing the mirror had loosened. The vehicle was repaired; however, the failure persisted. The manufacturer was not made aware of the failure. The failure mileage was approximately 38,000.