Over the past week, I've got this dead spot on the right side of my Mk II. It's the whole depth of the firebox, front to back for about 4" from the side.
I let things burn down and shoveled out any ash in that area, got it going again and it came right back.
The fire went out so I started right from scratch and this morning, I have the same dead spot even though I've got a rip roaring fire in the rest of the stove.
For the warmer weather, I switched over to pea but it was burning fine up until this week.