Sound output device resets to incorrect default on boot

[David Osolkowski]

Ubuntu version: 19.10 eoan
gnome-control-center:
  Installed: 1:3.34.1-1ubuntu2
  Candidate: 1:3.34.1-1ubuntu2
  Version table:
 *** 1:3.34.1-1ubuntu2 500
        500 http://us.archive.ubuntu.com/ubuntu eoan/main amd64 Packages
        100 /var/lib/dpkg/status

Expected behavior: Selected sound output device remains selected after a reboot, given that no hardware has been changed.

Actual behavior: Every time I reboot, the selected sound output device resets to the first entry in the list, "HDMI / DisplayPort". I only have a DisplayPort connection to a monitor that does not have speakers. I do have a 2.1 speaker system connected to Line Out. Oddly, this does not affect actual audio playback; I still hear sound even when the wrong output appears selected. However, controls like the mute button on my keyboard only affect the selected output, so they don't work until I go select the correct output again. This problem never occurred until I upgraded to 19.10 a few days ago.

ProblemType: Bug
DistroRelease: Ubuntu 19.10
Package: gnome-control-center 1:3.34.1-1ubuntu2
ProcVersionSignature: Ubuntu 5.3.0-23.25-generic 5.3.7
Uname: Linux 5.3.0-23-generic x86_64
ApportVersion: 2.20.11-0ubuntu8.2
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Sun Dec 1 16:06:09 2019
ExecutablePath: /usr/bin/gnome-control-center
InstallationDate: Installed on 2019-01-12 (323 days ago)
InstallationMedia: Ubuntu 18.10 "Cosmic Cuttlefish" - Release amd64 (20181017.3)
ProcEnviron:
 LANG=en_US.UTF-8
 PATH=(custom, user)
 SHELL=/bin/bash
 XDG_RUNTIME_DIR=<set>
SourcePackage: gnome-control-center
UpgradeStatus: Upgraded to eoan on 2019-11-27 (4 days ago)