Volume Control in UPnP Network Mode

I am using Audirvana on a MBP networked to an Allo DigiOne (Raspberry Pi with s/pdif out) connected to an older dac (MSB Gold Link). Ever since using this networked configuration, I cannot control the playback volume level using Audirvana. At first, I used Volumio on the DigiOne, but program took total control of the volume and I had to use its interface (or app) to raise and lower the volume because Audirvana would jump from almost silent to full volume.

I am now using DietPi, DigiOne software customized by Allo. With it, I have been able to use Audirvana to control volume, but the slider control (interface or app) keeps jumping toward increased volume - frequently to the maximum…

Could really use some help here! The sound is fantastic and i don’t think that I would have tried the networked Pi strategy If Audirvana and its filters were not available. Once the volume control problem is solved, I can get on to the fun tweaking part of audio.