Months I ago I applied WD40 on the hinges of the basement door to halt it's incessant squeaking. Since then the door keeps "straying" open, apparently because the floor is somewhat sloped. What can I do to end the door's wandering ways?

Pull the hinge pin on the center hinge if there are three. Lay it on a hard or concrete surface and give the shaft a sharp blow with a hammer. This will give the pin a slight bow and cause enough resistance to stop the door from moving.

That is the easiest way to do it,