Moodle - Redirect on /<a></a> after an update on admin panel

I have a Moodle application version 4.0.2 over Apache webserver, using PHP v8.0. After a login as administrator or submitting a change into administration panel, the application will redirects you on a really weird URI like &quot;example.com/admin/\&lt;a&gt;\&lt;/a&gt;&quot;. I searched a lot in order to fix this behaviour, someone said it&#39;s a permission problem, so I changed the entire data directory and application directory to &quot;0777&quot; as reported into the official documentation. Someone else said it&#39;s an Apache misconfiguration. That&#39;s it: &lt;VirtualHost 0.0.0.0:80&gt; ServerName example.com Redirect / https://example.com &lt;/VirtualHost&gt; &lt;VirtualHost 0.0.0.0:443&gt; ServerName example.com DocumentRoot /var/www/example.com/httpdocs ErrorLog ${APACHE_LOG_DIR}/error.log AcceptPathInfo On SSLEngine on SSLCertificateFile /etc/apache2/certificates/certificate SSLCertificateKeyFile /etc/apache2/certificates/certificate &lt;Directory /var/www/example.com/httpdocs/&gt; AllowOverride None Require all granted &lt;/Directory&gt; &lt;/VirtualHost&gt; Taking a deep look on what the application does, it seems like to return a 303 after a login/submit that brings you on the page https://example.com/admin/\&lt;a&gt;\&lt;/a&gt;. This stuff is driving me crazy, because I do not have any error or info log, neither an useful output from Apache itself.