The contact owns a 2021 Nissan Rogue. The contact stated while driving 25 MPH, the brake pedal was depressed to the floorboard without warning. The contact pumped the brake pedal to stop the vehicle; however, the vehicle failed to respond as needed. The contact coasted the vehicle to a stop and after the vehicle came to a complete stop, the brake functionality returned. The vehicle was taken to an independent mechanic where an attempt was made to replace the brake calipers; but the mechanic was unable to perform the repair. The contact stated that the failure reoccurred for a second time while driving at a slow speed. The vehicle was taken to a dealer where the vehicle remained 2 weeks; however, the dealer could not duplicate or diagnose cause of the failure. The manufacturer was not yet notified of the failure. The vehicle was not repaired. The failure mileage was approximately 43,000.