Duplicating a mesh with shape keys in blender cause blend shapes in Unity stuck at zero

I'm building clothes for my character in blender and to do this I have to duplicate some part of my character
(like the bottom for pants, feet for shoes...). My character has shape keys.
When I duplicate it along with the rig, the shake keys works perfectly also with the duplicate. The problem is: when I export both of them in Unity as fbx, the blend shapes of my original character works great, but the blend shapes of my duplicate are stuck at zero.
How can I resolve?

 

Have you found a solution?

I have a similar issue, where my duplicated mesh has no shape keys at all.

Inside Blender, they are shown and work independently of the "parent" mesh' shape keys, as expected. But the exported model inside Unity, shows only shape keys / blendshapes of the original mesh, not the dublicated ones. They just don't appear at all.