We discovered that a security update on Windows 10(KB5034441 ) and Windows Server 2022(KB5034439) fails with a Download error – 0x80070643.
Thanks to a reddit thread I discovered that this error message is wrong. This update tries to patch the recovery partition and fails to do so because it is to small. I was able to fix all machines so far by resizing the recovery partiton from 578MB to 878MB with GParted started from res rescuezilla media.
Afterwards the Update ran successfuly.