Tim Ardoin's post in Update 1.1 for 2024 stuck at 99% was marked as the answer
Hey everyone - good news. We were able to reproduce the problem locally, and a fix to the updater is now live.
The problem was during cleanup, and other than having to force the Updater app to close, should have no other adverse side effects (the update will have completed successfully, and no large files should be left behind).
Thank you very much for the reports and sorry for the inconvenience!