balena-sound: usb-connected sound card (FiiO E10K USB DAC) not working after 3.x upgrade

Describe the problem I’ve been running balenaSound for a long time using FiiO E10K USB DAC and the hifiberry-dacplus dtoverlay. I upgraded to from 2.4.10 to 3.1.5 today and the (USB-connected) DAC no longer works (no sound via Bluetooth or Spotify). If I push 2.4.10 back to the device, the DAC functions again. I can reproduce this at-will in case there are specific logs/commands that are needed.

To Reproduce Steps to reproduce the behavior:

1. Upgrade from 2.4.10 to 3.1.5
2. Play music via Spotify or Bluetooth

Expected behavior Sound from the USB-connected DAC

Screenshots N/A

Device information

• Board (hardware info): Raspberry Pi 3B+
• Device type (as seen in balenaCloud): Raspberry Pi 3
• balenaOS version: balenaOS 2.38.0+rev1

Also tested with a new application and updated OS:

• Board (hardware info): Raspberry Pi 4
• Device type (as seen in balenaCloud): Raspberry Pi 4
• balenaOS version: balenaOS 2.56.0+rev1

Additional context Add any other context about the problem here.

The following is seen in the logs:

29.09.20 21:28:19 (-0500)  audio  Setting audio routing rules. Note that this can be changed after startup.
29.09.20 21:28:19 (-0500)  audio  Routing 'balena-sound.input' to 'balena-sound.output'.
29.09.20 21:28:19 (-0500)  audio  Routing 'balena-sound.output' to 'alsa_output.Audio.analog-stereo'.
29.09.20 21:28:20 (-0500)  audio  W: [pulseaudio] main.c: This program is not intended to be run as root (unless --system is specified).
29.09.20 21:28:21 (-0500) Service exited 'multiroom-client sha256:92079dc95a6a84aacefbb2fdc761c221ac77b2a7f88c92ebd2d86b48fd67f4d4'
29.09.20 21:28:21 (-0500) Service exited 'multiroom-server sha256:8e21445db079ab86d1f26fc2635b5a623d6827739182383feba502e6af551f74'
29.09.20 21:28:22 (-0500)  upnp  Ready for rendering.
29.09.20 21:28:22 (-0500)  airplay  Waiting for audioblock to start...
29.09.20 21:28:22 (-0500)  audio  E: [pulseaudio] module-loopback.c: No such sink.
29.09.20 21:28:22 (-0500)  audio  E: [pulseaudio] module.c: Failed to load module "module-loopback" (argument: "source="balena-sound.output.monitor" sink="alsa_output.Audio.analog-stereo""): initialization failed.
29.09.20 21:28:22 (-0500)  audio  E: [pulseaudio] main.c: Sink alsa_output.Audio.analog-stereo does not exist.