I found this on the fourm. I hope it helps. Read the last part.
First, a few technical details not mentioned in the manual that should be useful for understanding. maintaining, and troubleshooting a Tile Fire/Sherwood.
The first pic is the secondary chamber baffle at the top of the firebox. There’s a lot going on in this chamber so it deserves a close look. The air/flame/smoke gets mixed together while being pulled through the holes on their way to the chimney pipe. This ‘forced mixing’ is not common in more modern stoves, which instead provide an excess of air to aid secondary combustion.
The next pic is a tad out of focus and requires some explanation. It is looking through the chimney connector to the inside of the secondary chamber. The mirror is positioned so you can see inside toward the front of the chamber. There you can see a steel plate (B) which is placed a couple inches behind the holes and covers all but the outer 2.5†on either side. The flames/air/smoke gets pulled through the holes and is forced to mix in this ‘mini-chamber’ before exiting through the small openings (A) on either side of the plate into the larger chamber and then out the chimney. Simple but effective.
Tom Oyen gave good instructions on checking the damper control rod in this thread:
https://www.hearth.com/talk/threads/65588/
The next two pics show the bypass damper in open and closed positions. Yours should be able to move between these two positions easily. The steel plate serves as a stop for the damper in full open position. The damper “puck†floats on the baffle surface and on the control rod end (i.e. it is not attached to the rod) so it should accommodate a reasonable amount of warpage of the chamber bottom.
One thing about this secondary chamber is that a significant amount of fly ash accumulates up there with use. My stove accumulated 3 shovels full of very fine ash in 10 or so seasons of mild use. That’s quite a lot. Cleaning/vacuuming out the ash should be a part of your annual maintenance.
I first used a plastic kitchen spatula to scoop the ash into the firebox below. While doing so, I unknowingly pushed some of the ash between the damper “puck†and the steel plate. I then tried operating the damper control rod, and it was binding toward the full open position. Odd, since it wasn’t binding before I cleaned. So I vacuumed out the area behind the puck, and then it operated smoothly again. So if yours is binding, clean out this area in front of the plate before you pronounce your baffle warped.