Referenced Rig Not Using Shader Overrides

[lms2k]

I have a character rig animated in a scene.  I need a render layer with an override on the shader for the ambient occlusion pass. 

It works on the referenced set in the scene so I thought it wasn't a reference issue. I did, however import an animated version of the rig, to then be referenced by the pre-existing reference of the rig in the scene in order to save time. I can't see this restricting me however.

Material override does not work either. In the script editor it says things like:

# Warning: Node 'Scene_09_Walk:Character:Cuff_RShape.instObjGroups[0].objectGroups[1]': cannot make assignment to 'aiAmbientOcclusion1SG' shader. #

For convenience of other circumstances, I need the AO to be a render layer, not an AOV.

Thanks for any assistance. 

[lms2k · Accepted solution]

I found out it would not let me edit the materials because the import was working off the reference while the reference was unloaded. So I loaded the reference, put it and the import in the collection and then the override worked.

I do not suggest importing for such a situation, seems a bit messy.