when I change background sometimes, ubuntu-18.04.5 hung

[Seiichi Nakashima]

I use Ubuntu-18.04.5 at my PC.
I want to change background, I select to Settings -> Background,
to change Background and Lock Screen, then I close Settings.

I operate to change background 2 or 3 times, ubuntu-18.04.5 hung up.
I power off/on PC, then recovered.

I oparete again, then same situation occur, I report bug
---
ProblemType: Bug
ApportVersion: 2.20.9-0ubuntu7.16
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: nakasima 1526 F.... pulseaudio
 /dev/snd/controlC0: nakasima 1526 F.... pulseaudio
CurrentDesktop: ubuntu:GNOME
DistroRelease: Ubuntu 18.04
InstallationDate: Installed on 2020-05-24 (90 days ago)
InstallationMedia: Ubuntu 18.04.4 LTS "Bionic Beaver" - Release amd64 (20200203.1)
IwConfig:
 enp2s0 no wireless extensions.

 lo no wireless extensions.
MachineType: To Be Filled By O.E.M. To Be Filled By O.E.M.
Package: linux (not installed)
ProcFB: 0 nouveaudrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-5.4.0-42-generic root=UUID=13e59966-6c10-4c26-b9f3-99ec6b187503 ro ipv6.disable=1 quiet
ProcVersionSignature: Ubuntu 5.4.0-42.46~18.04.1-generic 5.4.44
RelatedPackageVersions:
 linux-restricted-modules-5.4.0-42-generic N/A
 linux-backports-modules-5.4.0-42-generic N/A
 linux-firmware 1.173.19
RfKill:

Tags: bionic
Uname: Linux 5.4.0-42-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo
_MarkForUpload: True
dmi.bios.date: 11/08/2011
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: P1.10
dmi.board.name: 880GM-LE FX
dmi.board.vendor: ASRock
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: To Be Filled By O.E.M.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrP1.10:bd11/08/2011:svnToBeFilledByO.E.M.:pnToBeFilledByO.E.M.:pvrToBeFilledByO.E.M.:rvnASRock:rn880GM-LEFX:rvr:cvnToBeFilledByO.E.M.:ct3:cvrToBeFilledByO.E.M.:
dmi.product.family: To Be Filled By O.E.M.
dmi.product.name: To Be Filled By O.E.M.
dmi.product.sku: To Be Filled By O.E.M.
dmi.product.version: To Be Filled By O.E.M.
dmi.sys.vendor: To Be Filled By O.E.M.

[Seiichi Nakashima (ubuntu-linuxer)]

apport information

[Seiichi Nakashima (ubuntu-linuxer)]

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[Seiichi Nakashima (ubuntu-linuxer)]

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[Seiichi Nakashima (ubuntu-linuxer)]

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[Seiichi Nakashima (ubuntu-linuxer)]

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[Seiichi Nakashima (ubuntu-linuxer)]

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[Seiichi Nakashima (ubuntu-linuxer)]

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[Seiichi Nakashima (ubuntu-linuxer)]

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[Seiichi Nakashima (ubuntu-linuxer)]

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[Seiichi Nakashima (ubuntu-linuxer)]

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[Seiichi Nakashima (ubuntu-linuxer)]

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[Seiichi Nakashima (ubuntu-linuxer)]

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[Seiichi Nakashima (ubuntu-linuxer)]

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[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This change was made by a bot.

[Kai-Heng Feng (kaihengfeng)]

Can you please attach `journalctl -b -1` on the next boot from system freeze?

[Seiichi Nakashima (ubuntu-linuxer)]

Dear Kai-Heng Feng

I am nakashima

> Can you please attach `journalctl -b -1` on the next boot from system
freeze?

I see to send bug report attatching journal log.
Now, I use kernel 5.4.0-45, do not occur system freeze
to change background.