Terrain texture moves when camera moves

Hello,

I created a landscape, and applied a material (grass) to it (painting). I elevated some parts, but when I move, with the player or the camera, the texture seems to move as well, as if those squares that the original terrain were moving (by moving I mean they keep scaling up or down, therefore moving the grass texture with them).

Does anyone have any idea on how to stop that?

Thank you very much!!