Help 70-72 Duster owners

Thanks to all whom can help. I have a bench seat question. What keeps the seat back from coming off the seat bottom. I have male pins on the bottom and female on the seat back. Occasionally they will seperate. Look at picture. Any suggestions? I have new hinge covers and I dont want to break them. There were no covers before. Does the cover hold it on? Does not seem like a good option. Thanks Tod