• Entities don't cast shadow is they are in camera occlusion-culled region.
• Esp. underground: shadow holes caused by the objects that casts shadow being outside the light frustum's near clipping plane.
• Esp. underground, during sunrise and sunset: shadow holes caused by back-face culling.
• Extra: being able to limit shadow render distance reliably can help alleviate the cost of rendering more shadows to solve above issues.

Entities don't cast shadow if they are in camera occlusion-culled region.

Correction: Entities don't cast shadow if they are outside of camera frustum most likely. Terrain iterator seem to already have a routine to set shadow-visible region to "entities visible", so likely not occlusion issue.

Potential solution is to perform a second "should render" check using a shadow-aware frustum during entity rendering, and if passing despite failing the first check, render the entity as shadow extras only.