InResponseTo Atribute does not match Request ID

Hello everybody,
I have configured a WebSSO IDP in keycloak. Works wonderfully.

Now comes my problem. My application sends a SAML request to Keycloak let’s say with the ID=0.
Now the KeyCloak sends a SAML request to IDP Provider with the ID=1.
A SAML response comes back from the IDP with InResponseTo=1. So far everything is correct.

Now KeyCloak sends a response with InResponseTo=1 back to my application. And here it bangs.
My application discards the SAML response because InResponse Attribute does not contain the value 0 but the value 1. Does anyone know how I can correct this problem?

Is there a bug in Keycloak?

Thank you in advance

Yes, a bug.
…and one reason why I am still running KC 13… (amongst others, we are brokering MS 365 login to our local Shibboleth based SAML2 IdP…)