Been playing for 3 years now and I must say I've got a pretty good swing for someone starting at 32. Been obsessively videoing my swing in slow motion for a while now and I finally noticed the one thing I can tell is dramatically off: I tend to move my hips towards the ball in the downswing. I think it might even start a little bit in the backswing. I still keep my head "down" (as in I don't stand up before I impact), my shoulders stay in about the same place, but my lower back gets much more vertical than it should by the time I hit the ball. This is obviously causing lots of problems.
But my main question is, what's the cause? If there's a cause for this, I'd rather treat that than the symptom.