Strange distribution bug.

Working on my next map. I have drawn a trail using the material part of the editor soil for grass, and rough for dirt.

I made a "small trees" distribution but it only paints the trees on the "rough" terrain (the trail made in purple). The "soil" terrain is the main part of the map and the "rough" is the drawn out trail. What is going on? I tried with ferns and flower on a distribution but the same happened. But I use "small rocks" I can put those anywhere.

Image: https://i.imgur.com/Rnz072h.jpg

Oh blast, anything I can do? Otherwise I am having to hand place every single blasted plant.

Thanks for that, for now I have applied the "trail" material where I want to put distributions so it covers that up.

I had the same problem when I started my new map...I swapped the material selection i.e soil/grass to grass/soil and it fixed it.