Generated Lightmap UV scale

I’ve got problem with lightmaps generated inside UE4.
Meshes have 1st UV channel in good scale, but generating 2nd UV channel in editor rescales certain faces.

this is how lightmap density looks like:

and here you can see static mesh window:

Summarizing: 1st UV channel works just fine, but 2nd, generated inside UE4 doesn’t retain scale of faces.
Could someone help me with that?

Thanks in advance.

thats what you get for letting ue4 generate them. what you can do is create them in your second uv channel in your 3d package of choice and make sure everything (every uv-island) is 1:1 to eachother.
that way, even if you use that new 2nd uv channel to generate proper lightmaps from.

Unfortunately it doesn’t work for me. After making 2nd UV in blender and then in ue4 generating UV from 2nd channel to 2nd, I have the same results.
Small faces are scaled up.