Why are my imported models materials rendering with transparent holes?

I’ve tried to export from Blender to Unreal Engine. I also had the same issue of flipped normals, because of which my model looked transparent in some parts. I used two sided material and it fixed the issue. You could either go to Blender flip normals for those parts or add two sided option to your material.

I had a similar issue exporting mesh from Blender 2.8 to UE4.22 via .fbx.
Some of the faces become transparent in UE after importing. Normals in Blender was totally OK, but what i didnt noticed, i did not reset rotation and scale in Blender before exporting. When i did that, faces flipped automatically and turned my mesh to a total mess.
So before exporting from Blender dont forget to

  1. reset scale and rotation first, then
  2. check normals, then
  3. export.