I face same problem updating from 30.0.1 to 30.0.5, because a timeout in ssh i endup with step 9 in progress, if i remove the .step file the process fail at extracting (step6)
with
Extracting ...PHP Warning: require(/var/www/nextcloud/updater/../version.php): Failed to open stream: No such file or directory in phar:///var/www/nextcloud/updater/updater.phar/lib/Updater.php on line 699
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phar:///var/www/nextcloud/updater/updater.phar/updater.php(12): Symfony\Component\Console\Application->run()
#8 /var/www/nextcloud/updater/updater.phar(14): require('...')
doing this from here
rsync /var/www/nextcloud/data/updater-xxxx/backups/nextcloud-xxxx/ /var/www/nextcloud/ -av
Removing the .step file, running again
sudo -u www-data php --define apc.enable_cli=1 /var/www/nextcloud/updater/updater.phar
Finish the process and solves the issue
Thanks