Lighting artefacts, Light Leaking

Hello.

Does anybody know how to solve this thing? Iam using Baselightmass.ini in default setings with no changes and lightmass settings are- Static Lighting Level Scale: 0.15, Num Indirect Lighting Bounces: 20, Indirect Lighting Quality: 10.
There are no small artefacts when I change Static Lighting Level Scale to 1, but when I decrease the value, artefacts/lightleaks are appearing.
No matter what I do, with lightmass, or if I put box into the wall or under it or change mapping for lightmap, there is still one big light leak above the door and some small.
Iam using one sky light and few direct lights to lit the interior.

Thanks for any help

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