After doing the weekly cleaning of my pellet stove I decided that I would vacuum out the hopper. When I restarted the stove the burn pot filled up with pellets to the point that they were falling into the ash pan. It took longer for the pellets to start burning and when they did start the flames were really high for a few minutes. This only happens when I clean out the hopper. Is there something that I'm doing wrong? Or is there any way to prevent this from happening?