Volume control unreliable when used with Neutron DLNA renderer

I’m using A+3.5 to DLNA renderer app (Neutron player) on an Android tablet, to produce USB output to PS Audio DAC.

It plays and sounds excellent, but the Volume slider in Audirvana is a sometime thing.

I can’t figure out exactly makes it work, but sometimes it shows a No-slash across the speaker icon at its left end, and sometimes it lets you slide the slider, but to no effect.
Sometimes it starts working as designed if I select a different output device from the speaker icon and then set it back to the Neutron output, other times not. It takes 3-4 repeats of this sometimes to make the slider work.

I’ve also tried the USB Audio Player App as renderer, and it works too, but with no effect from the A+ volume slider. It also starts playing loud white noise after a minute or two.