To reproduce:

• Import a data type through the endpoint exposed by  DataTypeServlet::uploadDataTypes() with includeToModelImport set to true and model set to "ETSI SOL001 v2.5.1"
• Open the data type definition in the UI
• Add a property to the data type 
• Create a service using model "ETSI SOL001 v2.5.1"
• Download the csar for the service
• The definition of the imported data type is included in the Definitions/additional_type_definitions.yaml file in the CSAR, however the added property is not included