looks like you have no UVs specified for the heightmap so it is mapping to the entire landscape. I usually use worldposition-XY or sometimes landscapecoordinates for tiling textures. Worldposition-XY is more useful if you want to match the tiling on any static meshes near the terrain (ie common river border).
That is very strange that the selection outline is behaving differently. I have seen it do weird things before such as showing more intense displacement. For some reason the landscape must be using landscape coords in the vertex shader but UVs in the pixel shader as the default when no UV is specified. As long as you specify something it should fix it.