Volume Slide not working when playing to DLNA speaker

[fraserp]

Hi Guys
When casting to chromecast devices the volume slider on MM5 (on PC) works fine. But when I play to DLNA Samsung TV (to play through the soundbar) the volume slider stays at the very bottom and I can't control the volume from MM on the PC. When I lift the volume slider up (volume doesn't change) and when I let it go it just jumps to the bottom again. Any suggestions?

Running MM 5.0.4.2690

Fraser