If the update to UCS 4.4-5 aborts, the file
/var/log/univention/updater.log should be checked for the following error:
**** Downloading scripts at Thu Jun 25 11:34:04 2020 Error: Update aborted due to verification error: Verification error: Invalid signature: gpgv: keyblock resource '/etc/apt/trusted.gpg': File or directory not found
If the error appears in the logfile, all available errata updates should be installed, before starting the release update to UCS 4.4-5.
This issue will affect all UCS 4.4-4 systems that have a errata level between 605 and 641. Once the server version is UCS 4.4-4 errata 642 and above, a release update to UCS 4.4-5 is possible. The current errata level can be determined by running
univention-app info or in UMC by opening the side menu and clicking on Help -> About UMC.