weird cascaded shadow map behavior

“shadows nearest the player’s view have the highest resolution while those farthest away have the lowest. Beyond the range of the Dynamic Shadow Distance property, the system blends back into static baked shadows. In this way, you can take a scene with baked lighting and smoothly transition it to static baked shadows as you move away from objects.”

dynamic shadow distance = 2000, it works well

[video]- YouTube

dynamic shadow distance = 20000, it goes wrong

[video]- YouTube

u can see, shadow didn’t transit from dynamic to static…why?

ps: both scene were baked.

can someone figure it out, thanks very much.