Front Seat Belt Anchorage problems of the 1999 Chevrolet Tahoe

My 16 year old son was injured resulting from a side collision to our 1999 chevy Tahoe. The Tahoe was struck by a pickup truck traveling approximately 55 - 60 mph. The pickup struck the Tahoe on the driver's side of the vehicle behind the rear passenger door. The side window in the cargo area was broken by the impact and the Tahoe spun around. All four occupants of the Tahoe were wearing safety belts with shoulder harnress. My son was sitting in the back seat on the passenger side of the vehicle. The force of the impact appears to have caused the 60/40 rear seat to shift a fraction of an inch allowing the seatbelt harness to release where it attaches below the seat. When the seatbelt came apart he was thrown to the rear of the vehicle and his foot went through the broken side rear window. He sustained a severe laceration to his left foot severing tendons, ligaments and nerves. None of the other occupants of the vehicle were hurt as their seatbelts held secure. It appears the attachment which secures the buckle to the smaller rear seat requires a more substantial attaching pin. The 2000 model Tahoe has a bolt and nut that secures the buckle attachment whereas the 1999 model has a small pin with a flimsy press cap holding it in place.