Concise problem statement: Changing the layer settings results in the top & bottom layer becoming 'unconfigured', i.e. they are no longer visible in the layer toolbar.
Steps to reproduce bug:
Open the layer settings dialog.
Make a change - color or marking a layer configured. Save settings.
- To fix: Open source file and change the 3rd flag in the top & bottom layers to true.
Results: Top & bottom layer have disappeared from the layers toolbar.
Expected results: Top & Bottom layers to not be changed.