Middle row right seat belt keeps coming unlatched during normal operation. I ensure that it is latched correctly when I start driving. The passengers are not touching the seatbelt when it unlatches. We are notified that its unlatched by the seatbelt alarm. This started happening about three years after purchasing the vehicle. After happening several times, we took it to the dealer, who said they couldnt replicate the event. It happened again about a week later.