Because of well known water intrusion into the cabin from the firewall, over time the seat risers rust away, and then the compromised metal breaks, at which point the front of the seat is no longer bolted into the floor board. The seat swings backward uncommanded, and may is likely to startle driver, and cause crash. While the seat is swung backward, the driver has NO CONTROL OVER HIS POSITION IN THE VEHICLE. THE SEATBELT ALSO BECOMES COMPROMISED AS THE SEATBELT BELT BUCKLE IS CONNECTED TO THE SEAT ITSELF WHICH ITSELF BECOMES LOOSE FROM THE BODY OF THE VEHICLE. I have a video of the broken riser due to rusting over time due to the well known water intrusion issues. I can email you a video so you can see the danger of this issue.
NHTSA ODI 11658675