I may have a reasonable explanation after studying the design of this pellet drop system. All the others I have seen with a drop system have the fire pot in an open space below so that the fan can blow debris and ash away into the bottom of the pit. pg500 does, Louisiana type does, and the others as well. This pit has the pot in an enclosed chimney 7 inches high. Also the pellet drop opening is down almost to the fire pot. So if there is a pile up, of ash or pellet pieces, they don't have anywhere to go. Too much updraft is needed to carry them out of the chimney area. Doesn't take long for this to pile up into the pellet drop area. Since it is not wise to dump the pot while cooking, this will be a problem on long cooks. Especially with low temps and usually lower fan speeds.
I am going to call the seller today, and send mine back. I don't want to spend the next years trouble shooting this thing. Sorry for my mistake and enthusiasm.
Note: He called me after I submitted a cancel request to Amazon to inquire as to my reasons. He was very gracious and just wanted my input. He said that the fan speeds on low slow cooks might be too slow and that he would adjust the control so as to move out the ash. Perhaps he has communicated with you already about that. Also some additional adjustments were also implied.
Sorry for any ill advice I may have offered. I suspect that after his involvement with you those problems will be resolved. As for me, I will refrain from further comments but will be interested in following this page.