Here is what I did. Remove the door, and hinges as a unit. Then fill the screw holes with fibreglass, and polyester resin. As the resin jells us a razor to shave the excess off. This should leave the holes filled, but flush with the side of the trailer. Then tape the door back on so it looks right, (this took me three tries). Select new screws and get a drill bit that is just slightly smaller then the screws. Re-drill the holes, using the hinges on the door as a guide. Then glass and resin in the holes again, this time, while the resin is liquid screw new screws into the holes and let set.
Then on the door, pull one screw out to help select new screws. While the door is still taped in place fill the hole for the missing screw with glass and resin. Then put the new screw in. Repeat for all the screws in the door. You should now be good for another 20 years, or so.