I have 2 terrains modeled from blender and the textures I wanted uploaded just fine. The one problem is that on mobile the textures are messed up, but whenever I test on PC it’s fine.
The two images below show what the difference is, first one is the correct texturing (PC), and the second one is the mobile view.
I’m going to try to help you here, there are two things I think it could be. Make sure that the mound of grass is anchored, also if the mound and the grass are separated from each other I would select the grass and I would scale it up just a little bit so it’s not so thin. I hope this helps I’m not really professional when it comes to this but I think it won’t hurt trying.