We have an 8 year old Harman P68 that we've been having issues with the last few seasons. We are an indoor shooting range so with the ventilation for the range the shop is under some negative pressure, to the point it can be difficult to open the doors. I am not sure if this is our problem as we did not have any issues the first few years of running this stove. We thought adding an outside air intake would solve this, and it does seem to have made an improvement but did not solve all the issues. Right now the biggest issue is the stove does not seem to be blowing as hard as I recall it blowing before, and even with it cranked up on high i can physically hold my hand less then an inch from the stove. It is also leaving a lot of black soot and ash as opposed to grey/white we've gotten previously with the same pellets.