Light building artifacts

I have unnormal bug after build lighting,

256 is no where near large enough for a mesh this size, and the minimum lightmap resolution should not be the same as the lightmap resolution.

Use the lightmap density view and increase the lightmap resolution until it is at least green.

Realistically, you should not be importing this as a single mesh. It should be broken up into many different meshes so that their lightmaps can be divided up and atlas’d into multiple textures.

You should also ensure that you are building at production quality.

Already try.
Also set override lightmap resolution for mesh in level.

I don’t understand the dependence, but the reason was in the O UV channel, (main channel - NOT Lightmap channel) there was lot of inverted UVshells.
And lightmap channel (01) is generated correctly and does not have inverted shells.
I fix UVs and solve the problem.
Anyway, thank for your attention!