Thank you Seb Once I realised that mine was the only user account on my home desktop PC with this problem, I tried deleting all hidden config files that included the words "Nautilus" or "Gnome". This did not help so I created another sudoer and removed my home folder. I then recreated my home folder using cp /etc/skel. As explained in my earlier post, this action has removed the problem. I now feel that this issue is unlikely to be replicable by others. However in case it useful I followed your suggestion and put "journalctl -b 0" into a terminal and below is the result. I have only copies part of the output. I'm afraid I do not understand any of this myself. -- Logs begin at Wed 2020-04-29 19:21:25 BST, end at Mon 2020-05-18 16:42:40 BS> May 17 13:04:20 susan kernel: microcode: microcode updated early to revision 0x> May 17 13:04:20 susan kernel: Linux version 5.4.0-29-generic (buildd@lgw01-amd6> May 17 13:04:20 susan kernel: Command line: BOOT_IMAGE=/boot/vmlinuz-5.4.0-29-g> May 17 13:04:20 susan kernel: KERNEL supported cpus: May 17 13:04:20 susan kernel: Intel GenuineIntel May 17 13:04:20 susan kernel: AMD AuthenticAMD May 17 13:04:20 susan kernel: Hygon HygonGenuine May 17 13:04:20 susan kernel: Centaur CentaurHauls May 17 13:04:20 susan kernel: zhaoxin Shanghai May 17 13:04:20 susan kernel: x86/fpu: Supporting XSAVE feature 0x001: 'x87 flo> May 17 13:04:20 susan kernel: x86/fpu: Supporting XSAVE feature 0x002: 'SSE reg> May 17 13:04:20 susan kernel: x86/fpu: Supporting XSAVE feature 0x004: 'AVX reg> May 17 13:04:20 susan kernel: x86/fpu: xstate_offset[2]: 576, xstate_sizes[2]:> May 17 13:04:20 susan kernel: x86/fpu: Enabled xstate features 0x7, context siz> May 17 13:04:20 susan kernel: BIOS-provided physical RAM map: May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x0000000000000000-0x000000000005> May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x0000000000058000-0x000000000005> May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x0000000000059000-0x000000000009> May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x000000000009e000-0x000000000009> May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x0000000000100000-0x000000008b85> May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x000000008b852000-0x000000008b85> May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x000000008b859000-0x000000008c30> lines 1-23...skipping... -- Logs begin at Wed 2020-04-29 19:21:25 BST, end at Mon 2020-05-18 16:42:40 BST. -- May 17 13:04:20 susan kernel: microcode: microcode updated early to revision 0x27, date = 2019-02-26 May 17 13:04:20 susan kernel: Linux version 5.4.0-29-generic (buildd@lgw01-amd64-035) (gcc version 9.3.0 (Ubuntu 9.3.0-10ubuntu2)) #33-Ubuntu SMP Wed Apr 29 14:32:27 UTC 2020 (Ubuntu 5.4.0-29.33-generic 5.4.30) May 17 13:04:20 susan kernel: Command line: BOOT_IMAGE=/boot/vmlinuz-5.4.0-29-generic root=UUID=c977975b-e6da-444a-b063-5200452dc91f ro quiet splash vt.handoff=7 May 17 13:04:20 susan kernel: KERNEL supported cpus: May 17 13:04:20 susan kernel: Intel GenuineIntel May 17 13:04:20 susan kernel: AMD AuthenticAMD May 17 13:04:20 susan kernel: Hygon HygonGenuine May 17 13:04:20 susan kernel: Centaur CentaurHauls May 17 13:04:20 susan kernel: zhaoxin Shanghai May 17 13:04:20 susan kernel: x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers' May 17 13:04:20 susan kernel: x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers' May 17 13:04:20 susan kernel: x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers' May 17 13:04:20 susan kernel: x86/fpu: xstate_offset[2]: 576, xstate_sizes[2]: 256 May 17 13:04:20 susan kernel: x86/fpu: Enabled xstate features 0x7, context size is 832 bytes, using 'standard' format. May 17 13:04:20 susan kernel: BIOS-provided physical RAM map: May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x0000000000000000-0x0000000000057fff] usable May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x0000000000058000-0x0000000000058fff] reserved May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x0000000000059000-0x000000000009dfff] usable May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x000000000009e000-0x000000000009ffff] reserved May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x0000000000100000-0x000000008b851fff] usable May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x000000008b852000-0x000000008b858fff] ACPI NVS May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x000000008b859000-0x000000008c302fff] usable May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x000000008c303000-0x000000008c7fafff] reserved May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x000000008c7fb000-0x00000000aa02bfff] usable May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x00000000aa02c000-0x00000000aa433fff] reserved May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x00000000aa434000-0x00000000aa49bfff] usable May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x00000000aa49c000-0x00000000aa5defff] ACPI NVS May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x00000000aa5df000-0x00000000adffefff] reserved May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x00000000adfff000-0x00000000adffffff] usable May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x00000000af000000-0x00000000cf1fffff] reserved May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x00000000f8000000-0x00000000fbffffff] reserved May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x00000000fec00000-0x00000000fec00fff] reserved May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x00000000fed00000-0x00000000fed03fff] reserved May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x00000000fee00000-0x00000000fee00fff] reserved May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x00000000ff000000-0x00000000ffffffff] reserved May 17 13:04:20 susan kernel: BIOS-e820: [mem 0x0000000100000000-0x000000062fdfffff] usable May 17 13:04:20 susan kernel: NX (Execute Disable) protection: active May 17 13:04:20 susan kernel: e820: update [mem 0x8b699018-0x8b6b8a57] usable ==> usable May 17 13:04:20 susan kernel: e820: update [mem 0x8b699018-0x8b6b8a57] usable ==> usable May 17 13:04:20 susan kernel: extended physical RAM map: May 17 13:04:20 susan kernel: reserve setup_data: [mem 0x0000000000000000-0x0000000000057fff] usable May 17 13:04:20 susan kernel: reserve setup_data: [mem 0x0000000000058000-0x0000000000058fff] reserved May 17 13:04:20 susan kernel: reserve setup_data: [mem 0x0000000000059000-0x000000000009dfff] usable May 17 13:04:20 susan kernel: reserve setup_data: [mem 0x000000000009e000-0x000000000009ffff] reserved May 17 13:04:20 susan kernel: reserve setup_data: [mem 0x0000000000100000-0x000000008b699017] usable May 17 13:04:20 susan kernel: reserve setup_data: [mem 0x000000008b699018-0x000000008b6b8a57] usable May 17 13:04:20 susan kernel: reserve setup_data: [mem 0x000000008b6b8a58-0x000000008b851fff] usable May 17 13:04:20 susan kernel: reserve setup_data: [mem 0x000000008b852000-0x000000008b858fff] ACPI NVS May 17 13:04:20 susan kernel: reserve setup_data: [mem 0x000000008b859000-0x000000008c302fff] usable May 17 13:04:20 susan kernel: reserve setup_data: [mem 0x000000008c303000-0x000000008c7fafff] reserved May 17 13:04:20 susan kernel: reserve setup_data: [mem 0x000000008c7fb000-0x00000000aa02bfff] usable May 17 13:04:20 susan kernel: reserve setup_data: [mem 0x00000000aa02c000-0x00000000aa433fff] reserved May 17 13:04:20 susan kernel: reserve setup_data: [mem 0x00000000aa434000-0x00000000aa49bfff] usable May 17 13:04:20 susan kernel: reserve setup_data: [mem 0x00000000aa49c000-0x00000000aa5defff] ACPI NVS May 17 13:04:20 susan kernel: reserve setup_data: [mem 0x00000000aa5df000-0x00000000adffefff] reserved May 17 13:04:20 susan kernel: reserve setup_data: [mem 0x00000000adfff000-0x00000000adffffff] usable lines 1-58