Another beautiful map!

Welcome back :)

Looks very similar to the 1930s Overland Map style from the 2013 Cartographer's Annual.

https://www.profantasy.com/annual/2013/december13.html

I was able to replicate this issue, but only when I added the trees after I had already added the smoke.

The easiest solution is to delete the smoke and re-add it, or to move the smoke to a new sheet above the rest of the symbols. Perhaps calls it SYMBOLS Smoke.

I'm not sure if this is what would technically be called a bug, or intentional behaviour, so I will report it for you.

That looks better, but before you take the same texture any further down the same road, have you thought of switching the background to one of the other fills?

Yes - but not on any set timetable.