Shared pictures are not shown

Hello,
today I saw a problem with new shares on my nextcloud instance. A had version 17.x and upgrade to 18.x, but no change. I am using apache reverse proxy, this server is behind it. Thank you for some hints to fix it.

Nextcloud version: 18.0.1.3
Operating system and version :CentOS Linux release 8.1.1911
Apache or nginx version: Apache/2.4.37
PHP version: PHP 7.3.15
Steps to replicate it:

  1. I create a new folder.
  2. Upload a picture/pictures
  3. view pictures. Nice and working via log-in User
  4. Share this folder with “Read only”
  5. Sent a link to somebody
  6. After cliking, picture is set up for download. Not shown
  7. If I set “Hide download” after clicking on picture via shared link, nothing happend. Picture is not open/shown/downloaded.

config.php:

<?php $CONFIG = array ( 'instanceid' => 'xxxx', 'passwordsalt' => 'xxxx', 'secret' => 'xxx', 'trusted_domains' => array ( 1 => 'cloud.xxx.sk', ), 'trusted_proxies' => array ( 0 => 'xxxx', ), 'datadirectory' => '/var/www/html/nextcloud/data', 'overwrite.cli.url' => 'http://xxx/nextcloud', 'dbtype' => 'mysql', 'version' => '18.0.1.3', 'dbname' => 'xxx', 'installed' => true, 'dbhost' => 'localhost', 'dbport' => '', 'dbtableprefix' => 'oc_', 'memcache.local' => '\\OC\\Memcache\\APCu', 'dbuser' => 'XXXX', 'dbpassword' => 'XXXX', 'logtimezone' => 'UTC', 'theme' => '', 'loglevel' => '4', 'maintenance' => false, 'updater.release.channel' => 'stable', 'htaccess.RewriteBase' => '/', 'mysql.utf8mb4' => true, );