Hi, I have a couple of questions for you.
Is the over feeding of the pellets causing the stove to overheat? Or is the stove just not burning the pellets it is being feed? Do you notice a difference in the speed of the auger when you turn the speed down on the auger. Have you adjusted your restricter? Have you cleaned the vertical and horizontal exhaust duct? Have you cleaned the exhaust box and the exhaust blower fan and convection blower fan? Have you checked all vents to see if they are open? What I am getting at here is since your stove is not being shut down by the snap disk from overheating the stove is not burning the pellets. In other words if the auger was overfeeding the stove should be overheating?
Usually this is because of some kind of air flow restriction resulting in a build up of pellets in the stove that are not getting burned due to not enough air flow. The auger may be doing exactly what it suppose to be doing correctly. Even set to slow burn the stove is just not keeping up with the pellets it is being feed by the auger. I would check the areas I mentioned above. If your exhaust blower/convection blower are running properly check for air restrictions in the stove, flues, ducts, vents, etc;. It could be possible that someone has changed a setting on the stove. Resulting in giving the fire less air. This is what I would focus on first.
Now if the stove is trying to burn all the pellets it is being feed it would be overheating also if the auger was over feeding. If so, then we will have to look at another area?