I could be wrong... but this sounds very much like a problem that we've talked about before... with no indication of a resolution (that began occurring in the 2014 version).

Once you've loaded one of those demos, go to the mixer and check the plugins tab. Double-click the strings plugin setting to bring up the dialog. I don't think you need to do anything, but you might set it to "none". Then go back to the song and see if the RT plays...