Fbx import takes much longer in 4.19 as in 4.18.3

I wanted to import a larger fbx file to the UE4Editor. With 4.18.3 it takes around 5 minutes but with 4.19 it takes more than 4 hours to import the same file on the same computer. Did something change in fbx import feature within this versions?

So I had a deeper look inside of what is taking so much more time as before and I found out that the calculations of the overlapping vertices while building the skeleton mesh is the problem.

So in MeshUtilities.cpp inside of the BuildSkeletalMesh function the method UpdateOverlappingVertices was added and this takes very long if you have a lot of vertices. (My model has around 2.4 Millions)

Okay I have found how I could optimize my modell for faster import. I have seen that Unreal groups the vertices in sections with same material. For my modell I reduced the total number of materials to a minimum so a lot of vertices had the same material even if they belong to different objects. So the import goes much faster if I duplicate the material when used in different objects.
That is because the UpdateOverlappingVertices function does it work in quadratic time and for each section individual. In my model I had for instance one section with 2.4 millions of vertices and after my optimizations I had devided them in 50 sections. So the function could run much faster over the vertices.