I picked up another "bin" to hold bags of coal to let them unfreeze and drain. I place the bags upright and cut small holes in the bottom corners of the bags and let them sit over night. The second bin is an inexpensive green xmas tree container, and holds 5 50lb bags upright. The first batch of 5 bags produced just short of 5 gallons of water
which I measured by pouring into empty milk containers.
The DF520 is burning much better with the less wet coal now, but will keep checking it since I have started to dry out the coal before putting in the coal bin.
This seems like a science project.
However with the green second bin, I can now say I burn "green" coal.
EFM should offer a coal drying attachment similar to the salad drying mechanism:
So it appears the uneven burning is due to wet coal building up on the far side of the pot from the feed pipe too. Thanks for all the help and suggestions.