Redirect Untrusted URL Error

Hello,

I am trying to use rocketchat (not from the app store) via saml. Login is working fine but when I try to logout from univention (or from another service like nextcloud) I receive following error:

Nicht abgefangene Code-Exception

Eine nicht abgefangene Code-Exception ist aufgetreten.

SimpleSAML_Error_Error: UNHANDLEDEXCEPTION

Backtrace:
1 www/_include.php:17 (SimpleSAML_exception_handler)
0 [builtin] (N/A)
Caused by: SimpleSAML_Error_Exception: URL not allowed: https://chat.hla-flensburg.de/
Backtrace:
6 lib/SimpleSAML/Utils/HTTP.php:382 (SimpleSAML\Utils\HTTP::checkURLAllowed)
5 lib/SimpleSAML/Utils/HTTP.php:997 (SimpleSAML\Utils\HTTP::redirectUntrustedURL)
4 lib/SimpleSAML/Auth/State.php:281 (SimpleSAML_Auth_State::loadState)
3 lib/SimpleSAML/IdP/TraditionalLogoutHandler.php:106 (SimpleSAML\IdP\TraditionalLogoutHandler::onResponse)
2 lib/SimpleSAML/IdP.php:516 (SimpleSAML_IdP::handleLogoutResponse)
1 modules/saml/lib/IdP/SAML2.php:580 (sspmod_saml_IdP_SAML2::receiveLogoutMessage)
0 www/saml2/idp/SingleLogoutService.php:23 (N/A)

Ive added rocketchat to /etc/simplesamlphp/config.php like this (and restarted webserver)

'redirect.trustedsites' => chat.hla-flensburg.de,

How can I solve this issue?

Best Regards
LittleITworld

any thoughts on this? still havent figured out