[keycloak-user] What does "Session doesn't have required client" mean?

Hello, I have a question concerning Keycloak 4.8.3. I am using the spring security adapter to secure our web-app with the keycloak and enabled login feature: remember-me. The user logs in from a browser and it redirects back to out web app. Our web-app calls another Keycloak secured REST-API endpoint internally using the KeycloakRestTemplate, because we need to authorize these calls as well using the same user of the web app. After some amount of time the REST-API call fails with the following error message: "ERROR RefreshableKeycloakSecurityContext Refresh token failure status: 400 {"error":"invalid_grant","error_description":"Session doesn't have required client"}" and the keycloak log file contains the folowing warning: 17:25:51,929 WARN  [org.keycloak.events] (default task-1) type=REFRESH_TOKEN_ERROR, realmId=EHotel, clientId=IBE, userId=f:8db533c4-9733-48d4-8b30-28a50954b7ad:khaendel, ipAddress=192.168.1.76, error=invalid_token, grant_type=refresh_token, refresh_token_type=Refresh, refresh_token_id=9fba841f-54bb-4c81-8f7b-6a7e1c5ab92e, client_auth_method=client-secret I cannot predict when exactly that happens, presumably after 15 minutes or after an hour. Token expiration is set as follows: SSO Session Idle: 5 minutes SSO Session Max: 5 minutes SSO Session Idle Remember Me: 1 Day SSO Session Max Remember Me: 1 Day Access Token Lifespan: 2 minutes It seems, that there is a client session cache involved (InfinispanUserSessionProvider), that looses information after a while. What does the error message mean and what am i doing wrong? Please help me out. Thank you in advance, Regards, Ken