Let's take a minute and review.
The stove was working fine until a new brand pellet was introduced. Then a pro cleaning found a mostly clogged exhaust, cleaned it, and it ran for 3 days on the new pellets, then went back to the bad behavior.
Opening the combustion air gate did nothing. Changing the exhaust blower settings did nothing. Moving the wires to the back up sensor did nothing. The faults went from no ignition to fuel in the hopper.
Now there is a picture of the ash pan with fire burning up the pellets that should not be there.
One comment b Marina 1327 in reply #29 has my attention now.
All the time feeding pellets.
One question. Do you have a surge protector on the power supply cord? I apologize f this has been asked and I missed it. But with all of the inconsistent stove actions, I really am starting to believe the control panel is bad.
Given the picture already posted, the door seal, what bit of it is shown, looks fine. But the burn pot, just a short while of burning, is full of ash and clogged. there is fire in the ash pan and the ash pan has un-burnt pellet fuel in it. I dont think the pellets got there by too much air, though I can be wrong. By the looks of it, they got there from the burn pot over flowing. This could explain, IMO, why the exhaust was plugged, and may be plugged again. The control panel is over feeding pellets. Maybe not consistently, but at any given time it will over feed, smothering the fire which will smoke and cause the window to soot up, and begin clogging the exhaust.
Once the exhaust is partially clogged, this situation is exacerbated and the over feeding then really does smother the fire to the point of over flowing pellets into the ash pan. A faulty control panel may also cause differing faults that are inconsistent and cause other functions of the stove to malfunction.
I look forward to more pictures of the stove's condition to help confirm or deny some of this, but this problem needs solved and solved now.