Having issues with a surface layer after a Compute Terrain for lateral displacement. It's able to select geometry that isn't there and thus effects offsets and the scene. Where are these duplicated SSS shapes coming from? There is no low geometry there for the surface layer to even calculate at those areas outside the trench.
The surface layer attempting to grab the sides of the trench isn't even selecting the sides of the trench properly either.
It might be the Compute Terrain. If so, try using a much smaller patch size that is meaningful for the size of the landscape you're creating.