You have to have the 5 or six 1/4" or 5/16" holes in the feed auger tube to allow any gases to escape safely. Don't forget to cut the center notch for pot alignment pin either. Also, the alignment pin in the pot could be missing, so don't freak out if it has been broken off. Top dead center for the alignment notch.
See the posts on the breakdown of the S-20 pot and you know what it is suppose to look like. it is not fun to remove and retrofit the holes in that auger tube, but they are critical.
Sometimes wet coal will cake up fines in the feed tube holes also, but that is not part of your issue. You will not be able cover your coal bin, or extend the feed tube by the sounds, so more thought is required.
I assume the auger is in good shape also, if not this is a perfect time to replace it and the bushing.
Folks that have the coal source coupled that close to the pot have to be careful to cover the barrel or supply bin.
PS: Be really careful loosening the fasteners holding the tube to the pot, start spraying the penetrating oil early.....as you lay on you back wishing there were an easier way.