Thanks for the reply, Enplater.
I think I've eliminated wet wood as a factor: I've tried a burn with a second, older batch of wood splits from my wood shed, and even tried burning those sawdust bricks (sans chemicals or glue), but it just won't stay lit when I close the door.
I removed one layer (two of the four) baffles, and got marginally better burn performance: the fire would be sustained up to the point where I slightly latched the door, but when I went fully-closed, the fire still when out.
This weekend, my plan is to try a burn with the sawdust bricks and kiln-dried kindling with all the baffles removed. But before I try that, I'm going to take a recently-acquired, flexible endoscope and take a trip up the primary air supply. I remember reading the same thread that you mention, and I believe he said that his stove was actually replaced because of the issue.
If all else fails, I've gotten my old Fisher Mama Bear welded, and I'm going to try to install a baffle into that stove for a bit better performance & longer, cleaner burns.