Hi, I have created a simple scene with four walls and a window. I have an HDRI backdrop and a directional light. I have inserted a movable cube. After I bake the lighting I have the cube cut in half when in the middle of the room.
Here’s a screenshot.
This is light bleed from the volumetric lightmap (which is used to light movable objects)
You have two options: Make your walls/floors/ceiling a lot thicker, or decrease the VLM spacing in the lightmass settings. Preferably, some combination of both of those.