Microsoft has acknowledged two known issues in the Windows 10 Build 16299.125 (KB4054517). One is the error 0x80070643 and the second is update installation stuck at 99%. Microsoft has also provided workarounds for these two errors until the time it provides a final resolution.
Due to the error 0x80070643, Windows Update History reports that KB4054517 failed to install while the update gets installed successfully. This is what Microsoft has to say about this error.
Even though the update was successfully installed, Windows Update incorrectly reports that the update failed to install. To verify the installation, select the Check for Updates button to confirm that there are no additional updates available.
You can also type About your PC  in the Search box on your taskbar to confirm that your device is using OS Build 16299.15.
Microsoft is working on a resolution and will provide an update in an upcoming release.
For the issue of update installation stuck at 99%, Microsoft has provided a fix.
This workaround uses c:\temp and the x64 architecture as examples. Update these examples as appropriate for your environment.
- Download the appropriate version of KB4054022 for your device architecture from the Microsoft Update Catalog to c:\temp. Then run the commands in the steps below from the administrative command prompt.
- Expand the .msu file that you downloaded in step 1.
mkdir c:\temp
expand -f:* windows10.0-kb4054022-x64.msu c:\temp- End the existing Trusted Installer processes and install KB4054022 using the Deployment Image Servicing and Management tool.
taskkill /f /im tiworker.exe
taskkill /f /im trustedinstaller.exe
dism /online /add-package /packagepath:c:\temp\Windows10.0-KB4054022-x64.cab- (Optional) Delete the CBS logs from the Windows Logs directory.
del /f %windir%\logs\cbs\*.logMicrosoft is working on a resolution and will provide an update in an upcoming release.
 error 0x80070643 & update installation stuck at 99% provided by Microsoft){kind=link}