Despite your best efforts to make a lasting repair, a troublesome screw continues to loosen on a wobbly chair.

Remove the screw and dip the threads in epoxy, then reinstall it and let the epoxy dry. (Epoxy has more holding power than woodworker's glue.) If the screw hole has worn too large, use toothpicks or slivers of wood to help fill the opening.
—From the WOOD magazine shop