69below

Would need to see a video to pin point the problem, plus everyone has a different idea when it comes to swinging the club 'properly'. But I will say this...using a very aggressive lower body with half swing wedge shots is very difficult and will leave the club face open quite often. I would suggest hitting some balls with your feet together, getting the feeling of the club swinging very freely and making sure the club face is square at impact (ball should be starting on your intended target line). Make sure you swing through to a full finish that way you know you body is not too passive. Once you can do this comfortably, start speeding up and widen your stance. Always pay attention to where the ball is starting (no 45 degree right shots) and swing to a full finish. Need to get body and arms in sync.

http://www.golfchannel.com/media/swingfix-step-swing-drill/ This is a good one. Notice how he finishes with all his weight on his forward foot and completely facing the target.

I would check your left hand grip also, make sure it is more in fingers vs. palm. If your left hand (for a right hander) gets extremely weak you have to rotate your left hand very hard to square up the clubface. Very weak left hand makes it difficult to control the rotation.

Where and in what hand do you feel like this happens?