Same high take back every shot (even high balls). Drop the racket as you begin you swing and step forward (power step) with your body weight into the ball (very important never to have your weight falling back). Make contact.. SHANK!
.. make contact, supinate early.. SHANK!
These 2 occassions never deserted me for ages. I'm blaming "Step forward" and "suppinating early" all the effing time.