I find it hard to believe that you maintain spine angle on the way back, halfway down, and come up out of it at impact due to a swing flaw. You are maintaining the spine angle through the hard parts, most people loose it on the way back, but you loose it at the easy parts, at the stage where you are basically along for the ride. So, lets assume you maintained the spine angle that you are loosing. Well if your club is already getting down to the ball, if you maintained your spine angle at impact you would essentially be lower to the ground, right? Well if that was the case then after impact you would probably dig that club pretty deep, maybe as much as 3 or more inches. So, with the info that you have given, the first thing I would ASSUME is that you lift up so you dont dig deep trenches that hurt your wrists and possibly break your clubs, your body will naturally do things to protect itself. That is the primary reason for balance, so you dont fall down and hurt yourself. So IMHO, the things I would check first. Are you bent over too much, is the ball too far back, is there too big of an angle between left arm and clubshaft, does that angle need to be closer to a straight line. Always check the set up first, it is the easiet thing to change
my 02, good luck