We don't plan to work on this, users can use the GPU recompute tangent option for accurate normals with morph targets.
Unexpected vertex normal orientation when manipulating some morph targets.
This may be related to
UE-19861, but felt different enough to enter on it's own.
1. Import attached FBX (ensure Import Morph Targets is enabled)
2. Open the mesh in Persona
3. Bring up the Skeleton Tree and select Bone008
4. Rotate it +90 degrees around the Z axis
5. In the morph target list, adjust Box004 to a value of 1
6. Check the normals around the pelvis.
7. Import the same fbx into Maya and perform steps 3-6
Result: Maya handles the vertex normals as expected, but UE4 normals become reversed and oriented in unexpected directions
Expected: Similar or close to the same normal orientation as Maya when manipulating normals
Head over to the existingAnswerHub thread and let us know what's up.