KB5074109 causes apps accessing OneDrive or Dropbox to freeze. Outlook hangs on startup or fails to reopen without task kill or reboot. Users lose access to emails and inbox. Problem hits Windows 11 23H2, 24H2, 25H2, Windows 10 22H2, LTSC, and Servers 2019-2025. Microsoft confirms update as cause and monitors it. No fix timeline provided. Affects home users and businesses with downtime risk. Testing process fails repeatedly. Updates meant for security introduce critical bugs. Microsoft pushes paid support instead of quick fixes. Firms must pause updates increasing vulnerability. Prior issues included Remote Desktop crashes, Outlook problems, hibernation failures.