I think I’ve finally puzzled this one out. The issue is that when using the DS with BubbleUPnP, with it setup to control the volume of external renderers, volume control sometimes works, and at other times, has no effect.
I had thought that this loss of sync was caused when I used an IR remote to directly control the DS volume, but at times I’ve gone from using the remote to using the Bubble volume control, and it worked fine.
I now believe that the issue is simply time-dependent: if you try to set the volume from the Bubble slider several times in a short time, the DS will usually stop responding, and will no longer work from Bubble for “a while”. A secondary symptom of this is that the DS display will no longer visibly blink off and refresh a few seconds after you try to change the volume from Bubble.
If, when in this state, you leave Bubble alone for “a while”, it will often regain the ability to control the DS volume. I have not yet determined how long “a while” is, but it’s measured in minutes.
Can anyone else confirm or disprove this theory about the issue, or have I lost it completely?