Lighting does not properly affect landscapes under another landscape, even if Static Lighting Resolution is increased

Lighting does not properly affect landscapes that are below another landscape, even after static lighting resolution is increased. This results in some areas that should be completely shadowed to have light and large shadow splotches to appear along seams.

1. Open editor (any project)
2. Create 3 new landscapes
3. Layer the 3 landscapes in viewport so that one is at a higher point than the others, but each receives some light from a directional light.
4. If no directional light is in level, place one.
5. On the landscapes, Increase Static Lighting Resolution to 20
6. Build Lighting