Hi guys.. I've been running a Lopi Berkshire for the past 4 seasons and really like the stove. At the end of the '11 heating season I noticed some scant soot build up inside the stove and on the glass to a small degree. Cleaned it and ran it last season. Now as I clean and begin to ready for this winter I am again cleaning and noticed quite a bit of soot on the glass and on the floor and inner walls of the unit.. What is the problem ?