With Shadows set to All, there is a random object in the sky that is casting a medium size shadow on the ground even though there is nothing in the sky:
That’s the shadow hitting the bottom of the skybox. Move your camera so that the baseplate shadow and character shadows overlap. Weirdness all around, and apparently no one has thought of fixing it.
Supposedly this is the back-ray tracing because of how the Ray-traced shadow algorithm works. You can blame it on that, basically how it goes is:
For every vertex of a shape, there is a ray cast away in the opposite direction from the direction of the difference in position of the vertex and the sun. When the ray hits a face of a rendered object (Presuming the sky-box is one of face holding objects that is counted) it creates a shadow.
In all honesty, i would like to create my own shadow casting algorithm in the near future, when i wrap my head around a better way to make it because the current way allows for more shadows than is required in the Ray-Traced shadow algorithms.