Windows 10 update failure Error 0x8000ffff

I have been trying to put my system in a state where it will update automatically without error.

Windows Update currently reports: 2020-02 Cumulative Update for .NET Framework 3.5 and 4.8 for Windows 10 Version 1903 for x64 (KB4534132) - Error 0x8000ffff
2020-03 Cumulative Update for Windows 10 Version 1903 for x64-based Systems (KB4551762) - Error 0x8000ffff

The next reboot seems to involve a roll back and a further reboot.

I have spent time trying to resolve this using various on line resources which include tips on checking out devices with the Device Manager, Windows shop settings & others. I spent some time wandering through the Event logs too; but it helps if you know a) where to look and; b) what you are looking for.

I found Microsoft's resolution pages which led me to SetupDiag, which told me my last update was successful:
Note: The 'Cumulative Update for Windows 10 Version 1903' update was re-run prior to running SetupDiag to make sure I had a fresh error, not post reboot/rollback.

SetupDiag v1.6.0.0
Copyright (©) Microsoft Corporation. All rights reserved.

Searching for setup logs...
Found C:\Windows\Panther\setupact.log with update date 24/09/2019 21:16:40 to be the correct setup log.

Gathering baseline information from setup logs...

SetupDiag: processing rule: CompatScanOnly.
...No match.


SetupDiag: processing rule: PlugInComplianceBlock.
...No match.


SetupDiag: processing rule: BitLockerHardblock.
...No match.


SetupDiag: processing rule: VHDHardblock.
...No match.


SetupDiag: processing rule: PortableWorkspaceHardblock.
...No match.


SetupDiag: processing rule: AuditModeHardblock.
...No match.


SetupDiag: processing rule: SafeModeHardblock.
...No match.


SetupDiag: processing rule: InsufficientSystemPartitionDiskSpaceHardblock.
...No match.


SetupDiag: processing rule: CompatBlockedApplicationAutoUninstall.
...No match.


SetupDiag: processing rule: CompatBlockedApplicationDismissable.
...No match.


SetupDiag: processing rule: CompatBlockedApplicationManualUninstall.
...No match.


SetupDiag: processing rule: HardblockDeviceOrDriver.
...No match.


SetupDiag: processing rule: HardblockMismatchedLanguage.
..No match.


SetupDiag: processing rule: HardblockFlightSigning.
..No match.


SetupDiag: processing rule: DiskSpaceBlockInDownLevel.
..No match.


SetupDiag: processing rule: DiskSpaceFailure.
..No match.


SetupDiag: processing rule: PreReleaseWimMountDriverFound.
..No match.


SetupDiag: processing rule: DeviceInstallHang.
...No match.


SetupDiag: processing rule: BootFailureDetected.
.No match.


SetupDiag: processing rule: WinSetupBootFilterFailure.
.No match.


SetupDiag: processing rule: FindDebugInfoFromRollbackLog.
.No match.


SetupDiag: processing rule: AdvancedInstallerFailed.
..No match.


SetupDiag: processing rule: AdvancedInstallerGenericFailure.
..No match.


SetupDiag: processing rule: FindMigApplyUnitFailure.
..No match.


SetupDiag: processing rule: FindMigGatherUnitFailure.
...No match.


SetupDiag: processing rule: FindMigGatherApplyFailure.
..No match.


SetupDiag: processing rule: OptionalComponentFailedToGetOCsFromPackage.
..No match.


SetupDiag: processing rule: OptionalComponentOpenPackageFailed.
..No match.


SetupDiag: processing rule: OptionalComponentInitCBSSessionFailed.
..No match.


SetupDiag: processing rule: CriticalSafeOSDUFailure.
..No match.


SetupDiag: processing rule: UserProfileCreationFailureDuringOnlineApply.
..No match.


SetupDiag: processing rule: UserProfileCreationFailureDuringFinalize.
..No match.


SetupDiag: processing rule: WimMountFailure.
..No match.


SetupDiag: processing rule: WimMountDriverIssue.
..No match.


SetupDiag: processing rule: WimApplyExtractFailure.
..No match.


SetupDiag: processing rule: UpdateAgentExpanderFailure.
.No match.


SetupDiag: processing rule: FindFatalPluginFailure.
...No match.


SetupDiag: processing rule: MigrationAbortedDueToPluginFailure.
...No match.


SetupDiag: processing rule: DISMAddPackageFailed.
..No match.


SetupDiag: processing rule: DISMImageSessionFailure.
..No match.


SetupDiag: processing rule: DISMproviderFailure.
..No match.


SetupDiag: processing rule: SysPrepLaunchModuleFailure.
..No match.


SetupDiag: processing rule: UserProvidedDriverInjectionFailure.
..No match.


SetupDiag: processing rule: FindSuccessfulUpgrade.
..
SetupDiag reports successful upgrade found.
This appears to be a successful update as the last operation was: OOBEBoot and the result was: success

SetupDiag found 1 matching issue.

SetupDiag results were logged to: .\SetupDiagResults.log
Logs ZipFile created at: .\Logs_2.zip

This had me foxed, the 'Cumulative Update for Windows 10 Version 1903' update doesn't seem to have created a log - or if it has, not where SetupDiag is looking in C:\Windows\Panther\setupact.log. SetupDiag's log contains:

Matching Profile found: FindSuccessfulUpgrade - 8A0824C8-TRUNCATED
SetupDiag version: 1.6.0.0
System Information:
    Machine Name = NONAME
    Manufacturer = To Be Filled By O.E.M.
    Model = To Be Filled By O.E.M.
    HostOSArchitecture = x64
    FirmwareType = PCAT
    BiosReleaseDate = 20160329000000.000000+000
    BiosVendor = BIOS Date: 03/29/16 19:52:49 Ver: 04.06.05
    BiosVersion = P1.80
    HostOSVersion = 10.0.17134
    HostOSBuildString = 17134.1.amd64fre.rs4_release.180410-1804
    TargetOSBuildString = 10.0.18362.323 (19h1_release_svc_prod2.190809-2149)
    HostOSLanguageId = 
    HostOSEdition = Professional
    RegisteredAV = Windows Defender
    FilterDrivers = FileInfo
    UpgradeStartTime = 17/09/2019 11:05:04
    UpgradeEndTime = 24/09/2019 21:16:40
    UpgradeElapsedTime = 7.10:11:36
    CV = QZdr+diQKEOvuNto
    ReportId = WITHHELD


SetupDiag reports successful upgrade found.
This appears to be a successful update as the last operation was: OOBEBoot and the result was: success

Last Setup Phase:
Phase Name: End
    Phase Started: 24/09/2019 21:13:48
    Phase Ended: 24/09/2019 21:13:48
    Phase Time Delta: 00:00:00
    Completed Successfully? True


Last Setup Operation:
Operation Name: Start suspended services
    Operation Started: 24/09/2019 21:13:36
    Operation Ended: 24/09/2019 21:13:40
    Operation Time Delta: 0:00:00:04.0000000
    Completed Successfully? True


Matching Profile found: FindSuccessfulUpgrade - 8A0824C8-TRUNCATED
SetupDiag version: 1.6.0.0
System Information:
    Machine Name = NONAME
    Manufacturer = To Be Filled By O.E.M.
    Model = To Be Filled By O.E.M.
    HostOSArchitecture = 1033
    FirmwareType = PCAT
    BiosReleaseDate = 20160329000000.000000+000
    BiosVendor = BIOS Date: 03/29/16 19:52:49 Ver: 04.06.05
    BiosVersion = P1.80
    HostOSVersion = 10.0.17134
    HostOSBuildString = 17134.1.amd64fre.rs4_release.180410-1804
    TargetOSBuildString = 10.0.18362.323 (19h1_release_svc_prod2.190809-2149)
    HostOSLanguageId = 
    HostOSEdition = Professional
    RegisteredAV = Windows Defender
    FilterDrivers = FileInfo
    UpgradeStartTime = 17/09/2019 11:05:04
    UpgradeEndTime = 24/09/2019 21:16:40
    UpgradeElapsedTime = 7.10:11:36
    CV = QZdr+diQKEOvuNto
    ReportId = WITHHELD


SetupDiag reports successful upgrade found.
This appears to be a successful update as the last operation was: OOBEBoot and the result was: success

Last Setup Phase:
Phase Name: End
    Phase Started: 24/09/2019 21:13:48
    Phase Ended: 24/09/2019 21:13:48
    Phase Time Delta: 00:00:00
    Completed Successfully? True


Last Setup Operation:
Operation Name: Start suspended services
    Operation Started: 24/09/2019 21:13:36
    Operation Ended: 24/09/2019 21:13:40
    Operation Time Delta: 0:00:00:04.0000000
    Completed Successfully? True


Matching Profile found: FindSuccessfulUpgrade - 8A0824C8-TRUNCATED
SetupDiag version: 1.6.0.0
System Information:
    Machine Name = NONAME
    Manufacturer = To Be Filled By O.E.M.
    Model = To Be Filled By O.E.M.
    HostOSArchitecture = 1033
    FirmwareType = PCAT
    BiosReleaseDate = 20160329000000.000000+000
    BiosVendor = BIOS Date: 03/29/16 19:52:49 Ver: 04.06.05
    BiosVersion = P1.80
    HostOSVersion = 10.0.17134
    HostOSBuildString = 17134.1.amd64fre.rs4_release.180410-1804
    TargetOSBuildString = 
    HostOSLanguageId = 
    HostOSEdition = Professional
    RegisteredAV = Windows Defender
    FilterDrivers = FileInfo
    UpgradeStartTime = 17/09/2019 11:05:04
    UpgradeEndTime = 24/09/2019 21:16:40
    UpgradeElapsedTime = 7.10:11:36
    CV = QZdr+diQKEOvuNto
    ReportId = WITHHELD


SetupDiag reports successful upgrade found.
This appears to be a successful update as the last operation was: OOBEBoot and the result was: success

Last Setup Phase:
Phase Name: End
    Phase Started: 24/09/2019 21:13:48
    Phase Ended: 24/09/2019 21:13:48
    Phase Time Delta: 00:00:00
    Completed Successfully? True


Last Setup Operation:
Operation Name: Start suspended services
    Operation Started: 24/09/2019 21:13:36
    Operation Ended: 24/09/2019 21:13:40
    Operation Time Delta: 0:00:00:04.0000000
    Completed Successfully? True

Background Information: I had a motherboard failure I addressed in December last year with a new motherboard, processor & RAM. I addressed errors flagged in Device Manager except an error reported for my AMD Ryzen porcessor cores. This seems to disappear when running in safe mode and I don't have a clue why - the machine is running fine. This might be a red herring, as it doesn't explain why SetupDiag is not finding the upgrade log - anyway, here it is

I would be grateful for your help fixing this problem please, or at least what I haven't included which you might need to give a helpful opinion on the problem & its resolution.

With my best regards, Paul.