SSO with saml2 : Http post-bind in local metadata is missing

Question

I followed the spring tutorial for setting up SSO with saml. My filterChain is looking like this:

 @Bean
open fun filterChain(http: HttpSecurity): SecurityFilterChain {

    val authenticationManagerBuilder = http.getSharedObject(AuthenticationManagerBuilder::class.java)
    val samlUserDetailsServiceImpl = SAMLUserDetailsServiceImpl()
    authenticationManagerBuilder.userDetailsService<UserDetailsService>(samlUserDetailsServiceImpl)
    val authenticationManager = authenticationManagerBuilder.build()

    http
            .authenticationProvider(samlAuthenticationProvider(samlUserDetailsServiceImpl))

    http
            .httpBasic()
            .authenticationEntryPoint(samlEntryPoint());

    http
            .addFilterBefore(metadataGeneratorFilter(), ChannelProcessingFilter::class.java)
            .addFilterAfter(loginSuccessFilter(authenticationManager), BasicAuthenticationFilter::class.java)

                  http
            .csrf()
            .disable()
            .authorizeHttpRequests()
            .requestMatchers("/saml*", "/*.gif", "/*.jpg", "/*.jpeg", "/*.png", "/*.jsp", "/*.js", "/*.css", "/console*").permitAll().anyRequest().authenticated()
            .and()
            .authenticationManager(authenticationManager)

    return http.build()

when logging in it jumps into the loginSuccessFilter (inherits from samlprocessingfilter) and there it gets stuck by checking the metadata post-bind, which is missing at this point and a SAMLException is thrown. The local metadata xml includes the post-bind and the base url is set in the metadataGenerator:

 @Bean
open fun metadataGenerator(): MetadataGenerator? {
    val metadataGenerator = MetadataGenerator()
    metadataGenerator.entityId = "com:project:brxm"
    metadataGenerator.entityBaseURL = "http://localhost:8080/cms"
    metadataGenerator.extendedMetadata = extendedMetadata()
    metadataGenerator.isIncludeDiscoveryExtension = false
    metadataGenerator.setKeyManager(keyManager())
    return metadataGenerator
}

I don't know why the post-bind is getting missing ? Thanks for any hint in advance