We bought a house a couple years back with a HB-42A installed. The unit has a 3 blower system installed in the base. Holes 1, 3, and 5 have fans installed, holes 2 and 4 are blanked over. All fans work, but I don't get any airflow out of the top...it's like the fans aren't even there. But when I turn the fans on (especially with the doors closed), the fire starts leaping around on the wood like it's being blown in a wind. It's almost like the blower air isn't going around the firebox, it's going into the firebox. Any ideas?