Boy, I certainly do not understand how this could be happening. Cripe, I just raced last weekend for 8 hours and 17 minutes in the Round the Bay Race and furled the Hooter at least 50 times (every time I tacked upwind) and not once did it furl wrong.
As I said in previous posts, you must be sheeting too much on the foot and not enough on upper part of the sail to cause such a problem.
Was the sail cut for the boat or did you get it second-handed?
Are you using the 1:2 ratio on the furler line or the 1:1? 1:2 is far superior. (see post above on how to do it.)
Have you been lubing the upper turning swivel? If it drags, that could cause the upper not furling as fast as the lower part of the sail.
Good luck,
Rick