Many missing polygons in imported scanned mesh!

Hi all,

I’m having an issue importing this scanned mesh into UE. I have this chunk of scanned geometry, which looks fine in Zbrush and C4d, importing with tons of polygons missing (see attached pictures). I tried importing as FBX, 3DS, OBJ and using the C4d Datasmith plugin. I also tried fixing and flipping the normals on the mesh both in C4d and in Unreal.
Anyone ever deal with this before? I am new to UE so I’m not sure if this is a common issue or an easy fix. As you can see, this model is around 8 million polys - I realize that’s pretty high. Any tips or advice would be super appreciated!