How do I resolve DISM error 0x800f081f with the correct version of Windows 10?

Running DISM to repair a problem with windows update, I keep encountering 0x800f081f. I have tried to point DISM back to the /Source, based on guidance from a few sites. However, I keep seeing getting the same error. I understand that the source needs to be the same version I am running. From the output of DISM below, it appears that I am running 10.0.17134.1, but the version I get from Microsoft's download tool is 10.0.17134.228.

Do I need to get an ISO for 10.0.17134.1? And if so, how do I get that from Microsoft? The only references I have found online to download 10.0.17134.228 are from third-party sites, which seems very risky to me.

Background info: This started while trying to resolve a problem with Windows update trying to install:

• 2019-03 Cumulative Update for Windows 10 Version 1803 for x64-based Systems (KB4489868)

I encounter this erroor:

• Some update files are missing or have problems. We'll try to download the update again later. Error code: (0x80073712)

I have downloaded the tool to generate a windows 10 ISO from https://www.microsoft.com/en-us/software-download/windows10/

After extracting the install.wim file from there, I run this DISM command:

• DISM /Online /Cleanup-Image /RestoreHealth /Source:WIM:c:\install.wim:2 /LimitAccess

Here is the output from DISM:

Deployment Image Servicing and Management tool 
Version: 10.0.17134.1 
Image Version: 10.0.17134.228 

[===========================85.0%=================         ] 

Error: 0x800f081f 
The source files could not be found. 
Use the "Source" option to specify the location of the files that are required to restore the feature. For more information on specifying a source location, see http://go.microsoft.com/fwlink/?LinkId=243077. 

The DISM log file can be found at C:\WINDOWS\Logs\DISM\dism.log