Using the 'Texture' property of a model, to retarget its textures, works for the colour map but not the roughness/metal map. Trying to retarget the roughness/metal map gives zero metalness.
1. Add a model with this URL (and scale it up) : http://djdrumphil.ca/hifi/BugReports/textureRetarget/sharedTexture_spherify.gltf Note that its metalness is working.
2. Copy the model by sliding it with alt pressed.
3. In the second model, copy the text from 'Original Texture' into 'Texture' and add 'retarget/' before the end of the filename. Note that it has zero metalness, even though the referenced rougness/metal texture is an identical copy.