My issue started when i realised that the non-playable area was to small, so i created a new bigger map and I stamped everything from the old map to the new one.
Everything that I stamped worked quite well except the terrain textures.
The starting "grass_base" texture on the new map seem to have replaced or been added above on some of my textures from the stamp.
Since I cant delete the starting texture because it's locked, I can't figure out any way to fix this except erasing the textures from majority of the map and repaint it again.
Here is what I mean:
This is how the textures look on the original file:

And this is how they look after I stamped the map to new one:

Not sure if it is clear enough but as you can see, the starting grass texture on the new map has somehow been placed above the textures from my stamp.