[Discuss-gnuradio] Stereo FM Radio Redux

Hello, all. I decided to revisit the implementation of a broadcast
(88-108 MHz) stereo FM receiver on my Ettus USRP E310. I found the
attached GRC flow graph on the web (I removed the RDS and waterfall plot
stuff). The radio works using the E310 as a USRP source but for some
reason the audio is mono (left and right channels are the same). I'm
running GRC on a computer linked to the E310 (remote mode). The
soundcard on the computer can play stereo audio fine, for example, from
Rhythmbox. Is something in the flow graph misconfigured or missing?
Your time and comment is greatly appreciated. Sincerely,

John Wood
U.S. Naval
Research Laboratory