I never had this error and the KB4571756 Cumulative Update installed normally for me. In the past there were times when the offline install worked when nothing else did.
Many online search results for this error code tie it to .NET 3.5 issues, which makes me wonder if installing/removing .NET 3.5 or a .NET Cumulative Update would help the situation. I do not have .NET 3.5 enabled at all on my system. But this could just
be a matching error code that shows up for .NET sometimes.
To remove .NET 3.5:
DISM /Online /Remove-Capability /CapabilityName:NetFX3~~~~
To add .NET 3.5:
DISM /Online /Add-Capability /CapabilityName:NetFX3~~~~
.NET 3.5 can also be added/removed by running optionalfeatures.exe, which launches the Turn Windows features on or off interface.
Latest .NET Cumulative Update September 8, 2020-KB4576478
https://support.microsoft.com/en-us/help/4576478
It sounds like doing an in-place "upgrade" to the same (or higher) Windows version as you
have installed has worked for some to resolve this. That is done by mounting the current ISO file for Windows 10 and running setup.exe. It keeps installed apps and files.