Lighting bleed in large scene

I am trying to build the large scene with 20 identical rooms.

(1) *Room contains one stationary spotlight with
intensity: 0.5, inner cone :90, outer cone: 90, and attenuation radius: 1800.

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(2) Level has stationary directional light with
intensity: 3.0, indirect lightning intensity: 1.0, volumetric scattering intensity : 1.0.

(3) Stationary Skylight with
indirect lightning intensity: 1.0, volumetric scattering intensity : 1.0.

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(4) LightmassCharacterIndirectDetailVolume, LightmassImportanceVolume and PostProcessVolume. Here is the light mass settings
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After the building the lighting i got these results.

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There is the lighting bleed in the corner as well as at the intersection of the walls.

(5) Here are the lightmass density sceenshots.
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It’s working with 4 Rooms. But Unable to work with 20 or more rooms.

I also tried to build the scene with UE 4.14 and UE 4.17. I got the similar results.