I'm trying to create a custom morph in Blender for CC3, but everytime I try and load the modified OBJ file back in, CC3 just crashes out. :(

My exact steps:
1. In CC3 - Modify character to Load Neutral Base
2. Export as OBJ (full body, no changes to Axis)
3. Import Obj to Blender
4. Sculpt a change - (just moved some point with the grab brush as a test)
5. Export Obj
6. Back in CC3, Create > Morph slider editor (Source morph set as Default Morph, Target Morph set as File and choose my modified OBJ. Use ObjKey from original export.
7. Click OK > Gets to 30%, then crashes out.

Can somebody tell me what steps I'm missing?

Many thanks