Microsoft released KB5034441 (Windows 10 21H2 and 22H2) or KB5034440 (Windows 11 21H2) to fix a BitLocker access issue found in Windows Recovery Environment.  This update fails on many computers and it is due to the partition on the drive that holds the Windows Recovery Environment (WinRE) software.  If there is not enough room (250MB of free space) in the partition the update will not install and will give you a 0x8070643 error.

Microsoft was aware of this issue an posted in the article about KB5034441 and KB5034440. Microsoft is working on a new update to resolve this issue and working to release that soon.  Microsoft released notes in Knowledge Base article KB5028997 on how to resize your WinRE partition so the update can install.  Depending on the space available on your hard drive this can lead to data loss if done incorrectly or if there is not contiguous free space to allocate more space to the WinRE partition. I would recommend waiting for the new update.

This update can also affect Windows Server 2022.