Bizarre Vermont Castings Defiant Issue

[mloring]

Going on my fourth winter with this temperamental beast. It's a Defiant 1975 CAT-C. Last winter I found a wad of what looks like ceramic insulation batting on the floor behind the stove, just below the air intake. Unfortunately I didn't get a picture of it. However, I'm getting the stove ready for this winter and need to solve this mystery. Where did it come from and is it something I need to replace? I got around back and under the stove today, and took some pictures of where it came from. There's still a wad of material stuck up in there. And I'm getting soot out of this opening when I clean the chimney. That can't be right. I do sometimes get some back drafts at night when the air intake is turned all the way down, which pops the griddle open and blows puffs of smoke out...another separate and frustrating issue with this stove. But could that have dislodged or blasted something open at the back of the stove? I've looked at the exploded diagram and it's no help whatsoever in figuring out what should be there. Any VC experts have experience with this?

 

[mloring]

Or maybe someone knows what the second opening above the air intake is for (this is where the wad of insulation came from and the soot falls out of)? It seems like this is an unrestricted opening for air into the chimney...which would explain why the two chimney fires I've had with this stove have been unextinguishable via restricting air through the primary air intake and damper.

I really can't believe this stove is legal to sell. Were it not for a well-designed chimney, it probably would have burned my house down by now.