Detail of the glue grooves and set screw holes in the joint body and pivot.

Sand the old glue off the pivot and joint body. Drill out the four glue holes in the joint body. Carve, file or grind a groove around the inside of the joint body connecting the glue holes, and in the plastic of the pivot. Be carefull to go around the metal of the pivot. I put several "stitch" grooves across the pivot groove to allow glue to flow into the grooves even if the body and pivot grooves didn't align perfectly.