In the hardware units, look and examine for apparent damage and weakness in the seat belts, buckles, latch plates and the guide loops of the child safety seats. Make sure the seat belt reminder light comes on during the ignition key in the RUN or START position. The seat belts are intended to restrain by 'locking up' during a stop or impact which, at the same time, should remain loose enough for free movement during normal driving; ensure that the retractors pull the belt in and up against your chest while driving and ensure that the belt reaches its full retraction when the buckle is released. If any of the check indicate a problem with the seat belt system then replace as many parts as needed.