When I've cleaned mine so far I've only actually cleaned the burn pot. I was looking at the owner's manual the other day where it mentioned cleaning the draft fan. Have you been doing that as part of your routine maintenance?
I clean mine only when the display tells me to, which is about every 800 hours of actual burn time.
Each time I clean it I pop the draft fan off first
Use a soft nylon bristle brush, 2" diameter down the flues to brush the dust off the scrapers mainly.
Brush off the draft "impeller" blades.
Then go to the firebox and start cleaning that from the top down.
Lift the diverter plate out of the top of the fire box and brush it off. Replace.
Brush down the sides of the firebox.
Vac out the ashes from the bottom.
Take the access plate off the second ash compartment under the flues and vacuum that area.
Brush and vacuum the firepot itself.
Remove the primary air ball and make sure there are no ashes in the air tube underneath it.
Remove the ash "suitcase" and dispose of ashes in there.
Replace everything and I'm done for another 6-8 weeks.
Since the first 2-3 tons, I do not even open the firepot door between cleanings. Just put pellets in it and let it do its thing......which it does exceedingly well.