I believe that my Fuel Filler Pipe Shield Assembly https://parts.lakelandtoyota.com/sho...hString=filler , onto which the fuel filler nozzle is designed to "hook," is just worn out after 24 years. Unfortunately, it is one of the few parts on MY truck that Toyota has discontinued.

But I don't think I would bother fixing it anyway. I live in California; it's not like I have to pump gas when it's -18°F.