this.background_music.url = "pkg:/sounds/snd_background_music.wma"
So your saying you verified this on another channel that loops?
If so that makes me feel better, if it effects multiple channels they should fix it soon.
"soon" with firmware updates could be weeks or even months, so you may want to look into adding your own looping functionality. It's easy enough to listen for the isFullResult() event and restart the stream.