Update to 19.0.13 - An error occured

Nextcloud version : 19.0.3 Updating to 19.0.13
Operating system and version : Don’t know - shared hosting
Apache or nginx version: Shared hosting
PHP version : 7.3.33

The issue you are facing:
Tried updating using the Web Updater - The error I get is: An error occured… Which is quite helpful.

Is this the first time you’ve seen this error? Yes.

Steps to replicate it:

Currently I can go into the config.php file and disable maintenance mode, so I can re-run the process. Which lead to the same result.

The output of your Nextcloud log in Admin > Logging:
Can’t login anymore.

The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):

$CONFIG = array (
  'dbtype' => 'sqlite3',
  'version' => '',
  'installed' => true,
  'app_install_overwrite' => 
  array (
    0 => 'joplin',
  'updater.secret' => 'something cryptic',
  'maintenance' => true,
  'theme' => '',
  'loglevel' => 0,

The output of your Apache/nginx/system log in /var/log/____:

There is no log.

I would also be fine with just canceling the backup for now.
Any help is much appreciated!