There may be some softened edges dividing the faces there. Turn on hidden geometry to check this out (View menu). Also, if the face bearing the texture is inside a group/component, you need to dig down to the face (edit the group).

Take a look at my 3-minute movie to see SketchUp in its full-4D glory.

Then use the code in my tutorial's Chapter 16 for classes that let you do all this without need for the APIs Transformation class.