Rear driver's side seat belt not fastening.
If the seat belt will pull all the way out but simply not fasten to the latch, the latch has been compromised. Removal of the rear seat will be required and a new latch from the manufacturer installed. I would recommend having a technician from YourMechanic perform this service as they are mobile. This way you will not have to drive with any passengers that are unsafe.
Have a car question? Get free advice from our top-rated mechanics.