sound devices disappear from sound settings

[Islam]

Sound devices disappear from the sound settings however sound is still working.
pulseaudio --kill pulse audio --start restore them back to the sound settings. In rear cases, it cannot be started "daemon startup failed".
This can happen at any time without a reason, also sometimes happen when plugging headphones or connecting bluetooth speaker.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: pulseaudio 1:8.0-0ubuntu3
ProcVersionSignature: Ubuntu 4.4.0-21.37-generic 4.4.6
Uname: Linux 4.4.0-21-generic x86_64
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
CurrentDesktop: Unity
Date: Tue Apr 26 01:02:04 2016
InstallationDate: Installed on 2016-04-24 (1 days ago)
InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
SourcePackage: pulseaudio
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 09/04/2014
dmi.bios.vendor: coreboot
dmi.bios.version: 4.0-6588-g4acd8ea-dirty
dmi.board.name: Peppy
dmi.board.vendor: GOOGLE
dmi.board.version: 1.0
dmi.chassis.type: 3
dmi.chassis.vendor: GOOGLE
dmi.modalias: dmi:bvncoreboot:bvr4.0-6588-g4acd8ea-dirty:bd09/04/2014:svnGOOGLE:pnPeppy:pvr1.0:rvnGOOGLE:rnPeppy:rvr1.0:cvnGOOGLE:ct3:cvr:
dmi.product.name: Peppy
dmi.product.version: 1.0
dmi.sys.vendor: GOOGLE

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Bruno Nova (brunonova)]

I'm seeing the same thing.

Every once in a while, the sound devices disappear from the sound settings.
However, for me the sound usually stops working, and then when I open VLC, it throws sound errors.

This bug seems to be important.

[Bruno Nova (brunonova)]

This is happening several times per day and is becoming annoying (I lose sound).

"pulseaudio --kill" fixes the sound ("pulseaudio --start" is not needed).

[Bruno Nova (brunonova)]

It seems my issue may be due to Firejail.
Here's a bug report in Firejail: https://github.com/netblue30/firejail/issues/69
There's also this one in Launchpad: https://bugs.launchpad.net/ubuntu/+source/pulseaudio/+bug/1572493