Apache2 strange 404 errors logs (in Base64)

Nextcloud: 28.0.5 (was the same in all NC 27.1)
OS: Debian GNUX/Linux 12 (bookworm)
Linux: 6.1.0-20-amd64 x86_64
Apache: 2.4.59 (Debian)
PHP: php-fpm 2:8.2 (redis 5.3.7)

Hello Nextcloud Community !

I’m going round in circles with some 404 errors in the access.log Apache logs exclusively done by Safari browser on iOS and iPadOS clients.
Here is an example of the error I got by the dozen when loading the splash login screen:

2001:0000:4136:e378:8000:63bf:3fff:fdd2 - - [28/Apr/2024:16:05:37 +0200] "GET /core/css/data/:image//svg/+xml/;base64/,PHN2ZyB3aWR0aD0iMTYiIGhlaWdodD0iMTYiIHZlcnNpb249IjEuMSIgdmlld2JveD0iMCAwIDE2IDE2IiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjxwYXRoIGQ9Im03LjkwNjIgMWE3IDcgMCAwIDAtNi45MDYyIDcgNyA3IDAgMCAwIDcgNyA3IDcgMCAwIDAgNy03IDcgNyAwIDAgMC03LTcgNyA3IDAgMCAwLTAuMDkzNzUgMHptMC4wOTM3NSAyLjY5OTJhNC4zIDQuMyAwIDAgMSA0LjMwMDggNC4zMDA4IDQuMyA0LjMgMCAwIDEtNC4zMDA4IDQuMzAwOCA0LjMgNC4zIDAgMCAxLTQuMzAwOC00LjMwMDggNC4zIDQuMyAwIDAgMSA0LjMwMDgtNC4zMDA4eiIgZmlsbD0iI2ZmZmZmZiIvPjwvc3ZnPgo/= HTTP/2.0" 404 5692 "https://cloud.example.com/" "Mozilla/5.0 (iPhone; CPU iPhone OS 17_4_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.4.1 Mobile/15E148 Safari/604.1"

This does not occur when using another browser like Brave or Firefox on the iPhone/iPad. Just with Safari.
(I do not have any MacOS device to make a Safari test with those).
This is not related to a Nginx reverse proxy, the 404 errors occur when iPhone/iPad directly connect to the NC Apache server !

Please kindly note that I am not encountering any error in the Nextcloud logs, even in debug mode.
I could live with these errors, as from the client side, everything seems to work fine, you can use Nextcloud in a perfect experience.
The issue is that these multiple 404 errors in the Apache access.log trigger security tools like Crowdsec (who monitors access.log), with consequence of banning the iOS/iPadOS IPs. So my only way was to totally disable crowdsec.

I made many searches to understand why these erros occurs, but I totally failed to find any clue.

Did you ever experienced such a strange thing ?
Do you have any idea on where it could come from ?

Many thanks for any advices.

Here is the Nextcloud configuration file:

<?php
$CONFIG = array (
  'instanceid' => 'ocxxxxx',
  'passwordsalt' => 'xxxxx',
  'secret' => 'xxxxx',
  'trusted_domains' => 
  array (
    0 => 'cloud.example.com',
  ),
  'datadirectory' => '/data',
  'dbtype' => 'pgsql',
  'version' => '28.0.5.1',
  'overwrite.cli.url' => 'https://cloud.example.com',
  'htaccess.RewriteBase' => '/',
  'dbname' => 'nextcloud',
  'dbhost' => 'localhost:5432',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'dbuser' => 'nextcloud',
  'dbpassword' => 'xxxxx',
  'installed' => true,
  'default_phone_region' => 'FR',
  'default_language' => 'fr',
  'default_locale' => 'fr_FR',
  'memcache.local' => '\\OC\\Memcache\\APCu',
  'memcache.distributed' => '\\OC\\Memcache\\Redis',
  'filelocking.enabled' => true,
  'memcache.locking' => '\\OC\\Memcache\\Redis',
  'redis' => 
  array (
    'host' => '/var/run/redis/redis-server.sock',
    'port' => 0,
    'timeout' => 0.0,
  ),
  'mail_from_address' => 'admin',
  'mail_smtpmode' => 'smtp',
  'mail_sendmailmode' => 'smtp',
  'mail_domain' => 'example.com',
  'mail_smtphost' => 'mail.example.com',
  'mail_smtpport' => '465',
  'mail_smtpsecure' => 'ssl',
  'mail_smtpauth' => 1,
  'mail_smtpname' => 'admin@example.com',
  'mail_smtppassword' => 'xxxx',
  'defaultapp' => 'files',
  'trusted_proxies' => 
  array (
    0 => '192.168.85.61',
    1 => '2001:0000:4136:e379:7000:52ae:4eba:cafe',
  ),
  'overwriteprotocol' => 'https',
  'simpleSignUpLink.shown' => false,
  'maintenance' => false,
  'logfile' => '/var/log/nextcloud/nextcloud.log',
  'loglevel' => 2,
  'enable_previews' => true,
  'preview_max_x' => 1000,
  'preview_max_y' => 1000,
  'preview_libreoffice_path' => '/usr/bin/libreoffice',
  'enabledPreviewProviders' => 
  array (
    0 => 'OC\\Preview\\TXT',
    1 => 'OC\\Preview\\MarkDown',
    2 => 'OC\\Preview\\PDF',
    3 => 'OC\\Preview\\MSOfficeDoc',
    4 => 'OC\\Preview\\JPEG',
    5 => 'OC\\Preview\\PNG',
    6 => 'OC\\Preview\\GIF',
    7 => 'OC\\Preview\\BMP',
    8 => 'OC\\Preview\\XBitmap',
    9 => 'OC\\Preview\\MP3',
    10 => 'OC\\Preview\\HEIC',
    11 => 'OC\\Preview\\Movie',
    12 => 'OC\\Preview\\MKV',
    13 => 'OC\\Preview\\MP4',
    14 => 'OC\\Preview\\AVI',
    15 => 'OC\\Preview\\MSOffice2003',
    16 => 'OC\\Preview\\OpenDocument',
  ),
  'theme' => '',
);

Here is the Apache site configuration file:

<VirtualHost *:443>
	ServerAdmin webmaster@example.com

	DocumentRoot /var/www/nextcloud

	ServerName  cloud.example.com
	Protocols h2

	<IfModule mod_headers.c>
	  Header always set Strict-Transport-Security "max-age=63072000; includeSubDomains"
	</IfModule>

	<Directory /var/www/nextcloud/>
	  Require all granted
	  AllowOverride All
	  Options FollowSymLinks MultiViews

	  <IfModule mod_dav.c>
	    Dav off
	  </IfModule>
	</Directory>

	ErrorLog ${APACHE_LOG_DIR}/error.log
	CustomLog ${APACHE_LOG_DIR}/access.log combined
	
	SSLEngine on
	SSLCertificateFile      /etc/letsencrypt/live/cloud.example.com/fullchain.pem
	SSLCertificateKeyFile   /etc/letsencrypt/live/cloud.example.com/privkey.pem

	<FilesMatch "\.(?:cgi|shtml|phtml|php)$">
		SSLOptions +StdEnvVars
	</FilesMatch>
	<Directory /usr/lib/cgi-bin>
		SSLOptions +StdEnvVars
	</Directory>
	
</VirtualHost>

SSLProtocol             TLSv1.3
SSLHonorCipherOrder     off
SSLSessionTickets       off

SSLUseStapling On
SSLStaplingCache "shmcb:logs/ssl_stapling(32768)"