There's an important catch to working with Smart Objects ...
in the old days, when we wanted to duplicate a layer, we'd drag the layer to the new layer icon or click Ctrl-J (or Layer>New>Layer Via Copy) . If you do this with Smart Objects, it will appear to work the same as before. But wait ... all is not the same back in witness protection. All you've done in copying the Smart Object is create a copy of the reference back to the same original. This can have some important implications later on in your work flow.
In order to make a copy of a Smart Object (that isn't linked to the original) when working in layers, try this instead:
- Use a selection tool to select all of the pixels, click Ctrl-A, or click on Select>All.
- Select Edit>Copy or Ctrl-C.
- Finally, click on Layer>Smart Objects>New Smart Object Via Copy.
Have fun ...