Hi @David Schmidt ,
Just to make sure, did you install the latest Servicing Stack Update (SSU) before attempting to install the KB5006669 update?
I've seen a few with problems installing this specific update, however not many solutions have been provided, here's one thread which has one which you could refer to:
https://community.spiceworks.com/topic/2336785-unable-to-install-kb5006669-on-windows-server-2016
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Best regards,
Leon