If memory serves correct, there's a set screw that holds the shift knob in place. I'd check to see if that is tightened.
Best advise! However use blue not red or green!What worked for me was to remove the set screw, undo the knob, (screw off counter clockwise), clean it, put a dab of blue lock tight on the shifter threads, and reinstall knob till tight. Then replaced the set screw snug, with a dab of blue lock tight on it. Problem solved.