PHP sessions expire after X minutes

Hello,

Since few days, I have a problem with my sessions with codeigniter.
They expire after approximately 16/17 minutes. Nothing change in my code and everything was working good before.

Sessions are generated like this :

PHP Code:

$this->session->set_userdata('user', $username); 


My autoload.php :

PHP Code:

$autoload['libraries'] = array('database', 'session'); 


My config.php :

PHP Code:

$config['sess_driver'] = 'files';
$config['sess_cookie_name'] = 'ci_session';
$config['sess_expiration'] = 7200;
$config['sess_save_path'] = NULL;
$config['sess_match_ip'] = FALSE;
$config['sess_time_to_update'] = 300;
$config['sess_regenerate_destroy'] = FALSE; 


My phpinfo (PHP Version 7.2.17) :



I guess there is a problem with the my config server.

Do you have any idea ?


Thank you