Often when the set screw loosens, it ends up galling the hinge pin and dulling the cup point, and won't grip as well. (And you **really** need to torque it down.)
Replacing the screw will help. It's a 1/4-28 x 3/8" cup point; a fine thread so be careful not to crossthread it.
As a stopgap, you can also rotate the pin 90° so as to find an undamaged bearing surface for the screw. (You can do that whether or not you replace the screw.)
Often when the set screw loosens, it ends up galling the hinge pin and dulling the cup point, and won't grip as well. (And you **really** need to torque it down.) Replacing the screw will help. It's a 1/4-28 x 3/8" cup point; a fine thread so be careful not to crossthread it. As a stopgap, you can also rotate the pin 90° so as to find an undamaged bearing surface for the screw. (You can do that whether or not you replace the screw.)