Steps to solve this issue
Blender:
- Set the Unit to Metric and the Unit Scale to 0.01
- Scale the Mesh 100 times larger.
- Select all bones (not the Rig, but the bones) and scale them 100 times larger.
- Select both Rig and Mesh.
- Export to fbx.
FBX Export properties:
- FBX 7.4 binary
- Main->Selected Objects
- Main->Scale: 1.0 and not using the “Scale all data…” button.
- Main->Forward: -Z Forward
- Main->Up: Y Up
- Main->Both Armat button and Mesh button selected.
- Geometrie->Apply Modifiers selected.
- Geometrie->Smoothing: Face or Edge (to avoid the smoothing group warning).
- Armatures->Only Deform Bones ticked (to avoid unnecessary bones on UE4).
- Armatures->Add Leaf Bones unticked (to avoid unnecessary bones on UE4).
UE4 Import properties:
- Skeletal Mesh ticked
- Import Mesh ticked
- Import Uniform Scale: 1.0
- Convert Scene ticked
- Convert Scene Unit unticked
Those steps allowed us to fix a Rig in order to not have problems with the PhAT.
I hope this will help you!