Large Movable Object in Interior Cannot Receive Stationary Spotlight

I placed a Movable default cube mesh (So this post is not about lightmap baking problem) in a static closed room mesh, and there’s a Stationary Spotlight as the only light source. As for now all things work fine like this:

The question is, when I scale up the movable cube (Cube_Scaling) in one or more axis, the direct dynamic light on the cube disappears, only indirect light contributed by volumetric lightmap remains, shown as image and video link below:

[YouTube - Large Object Cannot Receive Stationary Spotlight][3]

Besides, this problem also occurs on larger movable meshes without any scaling, including static meshes and skeletal meshes.

Until now I found two ways to make the cube receive direct light again, but they’re rather error-prone compromises and the culprit of the problem remains unknown:

  1. Remove the “roof” of the room, then I can scale up the movable cube as long as I want:

  1. Reduce the Bound Scale of the movable cube below 1, but it makes the cube’s dynamic shadow incomplete:

It’s a fresh new blank project and I followed every instructions on official lighting guide, all lighting components are properly set.

Is this some kind of optimization side effects or simply a bug? Any help is appreciated.