If you delete a RadDiagramShape property using the SettingsPane (e.g. StrokeThickness) and then you try to call RadDiagram.Save() method, the generated string is not in the correct format. The deleted property is set to Auto in the string, while it should be set to 0.
Hence, if you try to load the same string, the RadDiagram throws FormatException.

Available in LIB version: 2014.3.1208