Missing XML "Words" and "TotalTime" properties after editing with "Word Web App"

I just discovered that some of the extended properties are now missing in documents after editing them using "Word Web App".

Previously these properties were correctly maintained while editing using the SkyDrive/Word Web App interface.  Recently editing a word doc using the web interface removes several properties from the schema.  This has been tested using IE10 and Chrome on Windows 8, and Firefox on Ubuntu.

The extended properties are accessed using the SDK as follows:

   stringsWords = pWordDoc.ExtendedFilePropertiesPart.Properties.Words;

   stringsTotalTime = pWordDoc.ExtendedFilePropertiesPart.Properties.TotalTime;

These functions should normally work, however after editing on the web now they fail because the properties are missing. 

Here are two samples of the app.xml contents from a document edited using desktop Word, and one after editing using Word Web App.  Again, the XML used to stay correct after editing on the web.

The XML in a correctly working Word document is in the docProps/app.xml file inside the document:

And here is the docProps/app.xml from a document after editing with "Word Web App":

 Several properties are now missing. 

Can someone explain what has happened to the properties because we were using them and now they are gone.

Thanks,

John