The log claims that the backup has been complete. There is no indication of anything being stuck. From what I see it looks like the redirection back to Joomla! Update to resume the core update is failing.
Since you already have a successful backup of your site prior to the update you can temporarily disable the Backup on Update feature to allow Joomla! Update to process the update without Akeeba Backup intervening to take a new backup before the Joomla! update.
At the bottom of the Joomla! Update page, in Joomla's status bar, you will see a green "BoU Active" message. Click on it. The page reloads, the icon turns gray and it reads "BoU Inactive". Now the Backup on Update feature is temporarily disabled. Proceed to running your Joomla! update. It will complete
without a new backup being taken.
Relevant documentation (for future reference):
Backup on Update
Nicholas K. Dionysopoulos
Lead Developer and Director
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