Keyboard and mouse lockup when using media keys to adjust volume

[Martin Brook]

Ubuntu 18.04 LTS
gnome-settings-daemon 3.28.1-0ubuntu1

Summary:
--------

When I press any of my keyboard's volume up/down/mute keys, my keyboard and mouse lock up completely. (Mouse pointer frozen and no keypresses have any effect). The rest of the system continues to function normally. The on-screen volume notification appears repeatedly every few seconds.

Variations:
-----------

Occasionally, I can press the buttons a few times with no effect, before the lock-up eventually happens.

Also occasionally, my Gnome session may crash completely to a black screen a few seconds after the input devices lock up.

I haven't been able to discern a pattern to when these different effects occur.

Troubleshooting attempted:
--------------------------

I can reproduce this when running from a Live USB on the same system.

Disabling the keyboard shortcuts for volume up/down and mute in the keyboard settings GUI does not prevent this issue.

If I set different keys for these shortcuts, they work fine - the problem is specific to my keyboard's special media keys.

The other (non-audio-related) media keys on my keyboard work fine.

I have gone through the suggested "Useful Information" steps at https://wiki.ubuntu.com/Hotkeys/Troubleshooting and will attach the output files to this report.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: gnome-settings-daemon 3.28.1-0ubuntu1
ProcVersionSignature: Ubuntu 4.15.0-20.21-generic 4.15.17
Uname: Linux 4.15.0-20-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.9-0ubuntu7
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Fri May 11 12:30:24 2018
EcryptfsInUse: Yes
InstallationDate: Installed on 2017-12-14 (147 days ago)
InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Release amd64 (20171018)
ProcEnviron:
 LANGUAGE=en_GB:en
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_GB.UTF-8
 SHELL=/bin/zsh
SourcePackage: gnome-settings-daemon
UpgradeStatus: Upgraded to bionic on 2018-04-27 (13 days ago)

[Martin Brook (martin.brook)]

Added a bit of additional troubleshooting info.

[Martin Brook (martin.brook)]

Still an issue in 19.04.

[Sebastien Bacher (seb128)]

Thank you for your bug report. Could you add your journalctl log after getting the issue?
Could you also give some details on the computer you are using? (is it a laptop? what model?)

[Martin Brook (martin.brook)]

Thanks for the reply. The PC is a desktop - Dell Precision Tower 5810.

However... I may have narrowed this down to something related to my Dell USB soundbar. I've disconnected it and the issue goes away.

The soundbar is a Dell AC511.

[Martin Brook (martin.brook)]

Here is the relevant part of `lsusb -v` for this soundbar.

[Launchpad Janitor (janitor)]

[Expired for gnome-settings-daemon (Ubuntu) because there has been no activity for 60 days.]