MorphTarget shading problem. Maya to Unreal

Hi, all. We’ve got problems with blendshapes and weird shading.

I know, that is a old problem, but nothign helps.
Elbow blends for example.

From maya
1/ lock-unlock normals?  -nope
2/ Average, Conform, set to face, soften edge - nope

Unreal 4.20 custom.
1/ Import normals - nope
2/ import normals and tangents - nope
3/ compute normals - nope


​​​​​​​Thanks for help