So, with the switch out of the box, unscrew the angled screws on the switch body
Push the rotator switch and body together twist anti-clockwise to separate top and bottom
THEN, re-install by pushing rotator switch into body and twist clockwise, (you'll feel it click into position) to "almost lock" into position
tighten the angled screws on side of switch body so they push the rotating switch part away from the body.
Note ONLY the black switch part should move, the silver colored outside ring doesn't move
see if top falls away from bottom.. should be no vertical play in between rotator switch and main switch body?