Microsoft ha released a compatibility fix to Windows Setup in Windows 10, version 2004, 20H2, and 21H1. 

KB5005932: Windows Setup Update for Windows 10, version 2004, 20H2, and 21H1: August 24, 2021

Summary

This update provides a compatibility fix to Windows Setup in Windows 10, version 2004, 20H2, and 21H1. This compatibility fix enables an in-place upgrade to be run on devices that cannot complete the installation of the latest cumulative update (LCU).

Known issues in this update

We are currently not aware of any issues that affect this update. 

KB5005932: Windows Setup Update for Windows 10, version 2004, 20H2, and 21H1: August 24, 2021