I have a tarm solo 60 wood boiler. Why is creosote suddenly building up on the interior of the loading door and surrounding area, sufficient to glue the door shut? I have been using this boiler for approximately six years with no problem. I recently changed the upper ceramic and lower ceramic tunnel. This had no beneficial effect. Wood moisture content is 8 - 10%. The dust was blown out of the blower fan and the chimney is clean. There seems to be a deficit of air flow at the half moon spaces at the top left and right of the door.