Hey ,
After some further investigation, I see what you mean. Maya/3dsMax handle the normals correctly (even from just the fbx), but manipulating them the same way in UE4 causes unexpected normal orientation (sometimes even reversed normals). I’ve reported this as UE-33456, but I noted some similarity to UE-19861, which reports that Morph Target Normals do not behave correctly when the Maya Blendspaces have locked normals.