See this post thread
https://community.ipfire.org/t/core-185-killed-my-ipfire-again/11523
and this post.
https://community.ipfire.org/t/core-185-killed-my-ipfire-again/11523/56
The issue is that the apache server did not get properly restarted in all cases after the upgrade was completed.
To be sure that the upgrade has completed you can check the upgrade log as per the above thread and then you can restart the apache server via the ssh connection or via the console.
However in all the cases in the above thread, if the system is still frozen after 10 minutes then the upgrade will have completed and rebooting will automatically restart the apache server.