Plugging in USB DAC results in volume being displayed as 20%, actually plays at 100%

Hello, I have an issue very similar to this one: When I plug in my Dragonfly Cobalt external USB DAC, whose volume I had previously set to 20%, and immediately start playing audio (e.g., playing a video on youtube), the audio will briefly play at 20%. Subsequently, at the same time as a popup on screen displays the name of the device, the playback volume will jump to 100% percent, with the GUI displaying the volume as 18%. Adjusting the volume by a single step, either using the software volume slider or the hardware volume controls, will immediately reduce the playback volume back to match what the GUI displays.
If I wait until the device name is display on screen after plugging in the DAC and only then start playing audio, the audio will immediately play at 100% and skip the brief period of normal volume playback (until I adjust the volume by a single step).

If I boot with the DAC already being plugged in, the initial playback volume will be 20% and stay at that level, until I make a single step volume adjustment (only tested with hardware volume controls), upon which the volume will jump to 100%. A further single step adjustment of the volume will drop the playback volume back to match what is displayed by the GUI.

I have tried adding a custom udev rule, to automatically perform the single step volume adjustment when the device is plugged in, but both the amixer and the pacmd commands do not work when run by root, as they result in the error “No PulseAudio daemon running, or not running as session daemon.”.

Any help would be much appreciated by me and my ears.