SAML does not work when set as only authentication method

Hello there,
I configured SAML as authentification method in RH-SSO.
It uses the Entra AD as IdP.
There is a Application Proxy configured in Entra, which is used so we have a gateway to the Internet.
The Problem is as follows:

If i set the Browser authentcation flow so that there is any other authentication method available, so you have to actively klick on the "saml button" in the login screen, it does redirect you to the Proxy authentification Login. Then you you can put in your Login information in and it works perfectly fine.

But if i disable all the other authentication methods, so that RH-SSO "automatically chooses saml" it just assumes some Login Informations and directly puts them into the Proxy Login, which fails.
Why does it behave so differently when i disable the other methods but works perfectly when i have other methods and i have to actively click the "saml button"?

Is a that a bug or how do i achieve the same behaviour in both instances?
I use Version 7.6, maybe a fix came out and i "just" have to update the System?