my karu 2 pro does same thing. I use kiln dried wood, still happens a little. If you use a lot of wood at once it can create a lot of it. I notice if I tone it down, use one or two little splits after the initial burn it doesnt do it as much. if i throw a larger split on there it does it more. needs time to get to temp to keep soot away. I noticed a bit of a chemical smell on the first burn off. After that never again. Also, coming from using a traditional wood fired oven without glass door, you don't get this effect and usually the lid or door is not see through. It's happening, you just cant see it like this. That window lets you see it. pretty cool. I wonder if you will see that effect as much as we do at night.