UPDATE: I called on Friday afternoon and spent about 45 minutes on the phone with Dennis.
He walked me through a few things and then had me put the MAK in to smoke mode with a clean fire pot.
He timed it and all was good there.
Next we set it to grill. Timed how long it took to get to temp and all good there.
He let me know that in the cool down sequence there is a pellet dump after 10 minutes and this may be causing the back burn.
We went in to cool down mode and he suggested I open the lid. The MAK was at 465 degrees when I did this with the lid open.
No problem!
So I guess I will be leaving the lid open (it is under a gazebo) during cool down.
Dennis is a great guy and I really appreciated his help.