St. Croix Greenfield pellet stove

Bought my stove 11 years ago and loved it until about 3 years ago. Now the pellets aren't burning completely and they're backing up in to the chute! Still burning! Have had service techs out so many times and they can't find anything wrong with it. I've adjusted the damper, draft trim, auger trim, even unplugged it to reset it. I clean it several times a week. Nothing helps. The techs said it MIGHT be the combustion fan, a $250 crap shoot! I will replace this POS for a reliable stove with a reputable company or hook back up to gas.