Support intro
Sorry to hear you’re facing problems 
help.nextcloud.com is for home/non-enterprise users. If you’re running a business, paid support can be accessed via portal.nextcloud.com where we can ensure your business keeps running smoothly.
In order to help you as quickly as possible, before clicking Create Topic please provide as much of the below as you can. Feel free to use a pastebin service for logs, otherwise either indent short log examples with four spaces:
example
Or for longer, use three backticks above and below the code snippet:
longer
example
here
Some or all of the below information will be requested if it isn’t supplied; for fastest response please provide as much as you can 
Nextcloud version (eg, 29.0.5): Nextcloud Hub 8 (29.0.3)
Operating system and version (eg, Ubuntu 24.04): Debian 12.6
Apache or nginx version (eg, Apache 2.4.25): nginx 1.26.1
PHP version (eg, 8.3): 8.3.8
Installed via docker image Linuxserver/nextcloud
The issue you are facing:
On File page with grid view, not all preview are shown. It needs multiple refreshes in order to replace all generic icon with actual previews as shown below:
Is this the first time you’ve seen this error? (N):
Steps to replicate it:
- Open a Folder with lots of images
- change to grid view.
The output of your Nextcloud log in Admin > Logging:
None relate to the operation with log level warning
The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):
<?php
$CONFIG = array (
'memcache.local' => '\\OC\\Memcache\\APCu',
'datadirectory' => '/data',
'instanceid' => '[removed for security]',
'passwordsalt' => '[removed for security]',
'secret' => '[removed for security]',
'version' => '29.0.3.4',
'overwriteprotocol' => 'https',
'installed' => true,
'default_phone_region' => 'GB',
'maintenance' => false,
'loglevel' => 0,
'theme' => '',
'filelocking.enabled' => 'true',
'upgrade.disable-web' => true,
'filesystem_check_changes' => 0,
'maintenance_window_start' => 1,
'remember_login_cookie_lifetime' => 2592000,
'session_lifetime' => 604800,
'memories.exiftool' => '/config/www/nextcloud/apps/memories/bin-ext/exiftool-amd64-musl',
'memories.vod.path' => '/config/www/nextcloud/apps/memories/bin-ext/go-vod-amd64',
'memories.vod.ffmpeg' => '/usr/bin/ffmpeg',
'memories.vod.ffprobe' => '/usr/bin/ffprobe',
'memories.gis_type' => 1,
'memories.db.triggers.fcu' => true,
'dbtype' => 'mysql',
'dbname' => 'nextcloud',
'dbhost' => 'mariadb:3306',
'dbport' => '',
'dbtableprefix' => 'oc_',
'mysql.utf8mb4' => true,
'dbuser' => '[removed for security]',
'dbpassword' => '[removed for security]',
'trusted_domains' =>
array (
0 => '[removed for security]',
1 => '[removed for security]',
2 => '[removed for security]',
3 => '[removed for security]',
),
'trusted_proxies' =>
array (
0 => '[removed for security]',
1 => '[removed for security]',
),
'overwrite.cli.url' => '[removed for security]',
'overwritehost' => '[removed for security]',
'mail_smtpmode' => 'smtp',
'mail_smtpsecure' => 'tls',
'mail_sendmailmode' => 'smtp',
'mail_from_address' => 'nextcloud',
'mail_domain' => '[removed for security]',
'mail_smtpauthtype' => 'LOGIN',
'mail_smtpauth' => 1,
'mail_smtphost' => 'smtp.gmail.com',
'mail_smtpport' => '587',
'mail_smtpname' => '[removed for security]',
'mail_smtppassword' => '[removed for security]',
'enable_previews' => true,
'preview_concurrency_all' => 72,
'preview_concurrency_new' => 36,
'preview_max_x' => 4096,
'preview_max_y' => 4096,
'jpeg_quality' => 80,
'preview_max_scale_factor' => 1,
'preview_max_filesize_image' => 50,
'preview_max_memory' => 256,
'enabledPreviewProviders' =>
array (
0 => 'OC\\Preview\\BMP',
1 => 'OC\\Preview\\GIF',
2 => 'OC\\Preview\\JPEG',
3 => 'OC\\Preview\\Krita',
4 => 'OC\\Preview\\MarkDown',
5 => 'OC\\Preview\\OpenDocument',
6 => 'OC\\Preview\\PNG',
7 => 'OC\\Preview\\TXT',
8 => 'OC\\Preview\\XBitmap',
),
'memcache.distributed' => '\\OC\\Memcache\\Redis',
'memcache.locking' => '\\OC\\Memcache\\Redis',
'redis' =>
array (
'host' => 'redis',
'port' => 6379,
'timeout' => 1.5,
),
);
The output of your Apache/nginx/system log in /var/log/____:
nginx error.log
Output errors in nextcloud.log in /var/www/ or as admin user in top right menu, filtering for errors. Use a pastebin service if necessary.
nextcloud.log