I post this here for visibility instead that the specific forum because I think is important...
The default "Normal Map Software Preset" in Preferences is "Unreal Engine"
And the default value for "Normal Calculation Method" is "Angle Weighted Normals"
That produces this normal map (first image) for a simple box kind of panel. That seems to be ok in UE4 but some artifacts appears when a "build lights" is performed there (I made sure this is totally unrelated to the infamous secondary uv channel need of unreal light-maps) as you can see in the left panel in the third image.
If I change the "Normal Calculation Method" to "3D-Coat Normals" then it works perfect! as you can see in the second image and in the third, in the right panel.
So I suggest that you 3d-coat developer/staff change that setting ("Normal Map Calculation Method") to default "3D-Coat Normals" if/when the "Normal Map Software Preset" is set to "Unreal Engine" so people like me don't waste time trying to figure out things, please
Thanks