I don't if it's a bug, but I think it's a bit strange behaviour.
When I tweak a material, for example, I change the diffuse slot from color to texture.
If the object is not a proxy => the modification is take in account immediately and is visible inside the ViewPort.

If the object is set as Movable proxy => nothing happens. I have to close the OctaneRender Viewport and restart to see the change.
Can you check this ?
Cheers