NAV 2013 R2
When I try this query I get the sales lines of the sales order, however none of the recently added fields to the 'Sales Lines' page show up.
The new fields do show in the RT client when viewing the sales order and they show up as columns in 'Sales Line' table.
I haven't found any additional properties, settings or documents that would explain the fields not coming through the OData web service. I've tried republishing the 'Sales Order' page and restarting the instance, but no dice.
If I publish the 'Sales Lines' page itself the fields do come through, but my understanding of the docs is that because it's a sub-page to the 'Sales Order' page, all fields should come through using containments as seen in the example URL above.
Using Containments and Associations - https://msdn.microsoft.com/en-us/library/hh167449(v=nav.71).aspx