Sounds like you were making syrup in the middle of your pan. Watch the bubbles and when it looks like syrup in the middle draw some off and dump it back into the pan behind the middle section to push it toward the draw off. Try running your pan a 1/2" deeper and fire consistently. You may be drawing off too slow too. Running a little deeper will help with that. I run mine at 1 1/2" and regularly start my draw at 7 and watch it go to 9 or 10 with the draw off wide open. I actually like doing it this way so that my syrup is heavy. I correct the density in my finisher before I filter and it is easier to thin it down with sweet from the front pan than it is to make it heavier in the finisher.