Hi Scott,
To resolve the KB5034204 update error, please delete or rename the folder C:$WinREAgent. Note that it's a hidden folder.
(solved) KB5034204 update fails - Microsoft Community: https://answers.microsoft.com/en-us/windows/forum/windows_11-wintop_update/kb5034204-update-fails/bdb89d8a-2765-4887-94ed-52f344df842f?messageId=d9cdfe38-afa3-4a29-81f8-71f62aba7a50