Animator is setting blend shapes to 0 (and overriding SetBlendShapeWeight)

If I have the Animator disabled, I can confirm the blend shapes are updating correctly (when I equip an item for example), however if I then enable the Animator the blend shapes get set to zero and I am unable to change them (even in inspector manually).

What is the cause of this?

I use Blender to export as FBX.

its happend to us now! WHY THIS ! DAMN IT WAS WORKING FINE NOW AFTER USE UMOTION our avatar customization blendshapes sliders are not working no more! some body give us an answear please!