Edit locally doesn't lock file: "not implemented"

Nextcloud version (eg, 20.0.5): 25.0.2
Operating system and version (eg, Ubuntu 20.04): Debian Bullseye
Apache or nginx version (eg, Apache 2.4.25): nginx 1.18.0
PHP version (eg, 7.4): 7.4

The issue you are facing: “Edit locally” opens the odt document locally but doesn’t lock it.

Is this the first time you’ve seen this error? (Y/N): Y

Steps to replicate it:

  1. Open webinterface
  2. Press the 3 dots
  3. Click “edit locally”

The output of your Nextcloud log in Admin > Logging:
There are no logs on the server side. Only on the client side the following shows up:

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

<?php
$CONFIG = array (
  'instanceid' => '***',
  'passwordsalt' => '***',
  'secret' => '***',
  'memcache.local' => '\OC\Memcache\APCu',
  'filelocking.enabled' => true,
  'memcache.locking' => '\OC\Memcache\Redis',
  'memcache.distributed' => '\OC\Memcache\Redis',
  'redis' => [
       'host'     => '/var/run/redis/redis-server.sock',
       'port'     => 0,
  ],
  'trusted_domains' =>
  array (
    0 => '***',
  ),
  'datadirectory' => '***',
  'dbtype' => 'mysql',
  'version' => '25.0.2.3',
  'overwrite.cli.url' => '***',
  'dbname' => 'nextcloud',
  'dbhost' => 'localhost',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'mysql.utf8mb4' => true,
  'dbuser' => '***',
  'dbpassword' => '***',
  'installed' => true,
  'theme' => '',
  'loglevel' => 2,
  'maintenance' => false,
);

So I wonder where I did miss the correct setting to enable the locking feature?