27 MB OBJ or FBX static mesh, Zbrush save 1s, marmoset reimport 0.3s, UE4 reimport 20s

Can someone tell me why reimporting an OBJ mesh into UE4 is so slow? I do this thousands of times while I work in Zbrush. I already put LOD group none, and disabled adjacency, computation of normals and tangents etc.

Have you checked the Output Log to see if there is anything out of normal happening after the import? Maybe something are causing unreal to take longer to processing.
Also the engine creates a *.UAsset file based on yout *.obj or *.fbx with lots of properties, optimizations, preparations, etc, different from modelling or model suites that read and display those format properties as soon as it get loaded.

Output log does not show any error. There is no justification for import taking this long unless the import function is written in javascript. As they keep piling on more feature I really with someone would look into this.