Why am I getting "Uncaught server error: java.lang.IllegalStateException: Can't add session: task in progress for session"?

Issue

Sometimes RH-SSO outputs following error when a user logout:

2020-12-10 16:46:12,539 ERROR [org.keycloak.services.error.KeycloakErrorHandler] (default task-1273) Uncaught server error: java.lang.IllegalStateException: Can't add se
ssion: task in progress for session
        at org.keycloak.models.sessions.infinispan.InfinispanKeycloakTransaction.put(InfinispanKeycloakTransaction.java:84)
        at org.keycloak.models.sessions.infinispan.InfinispanAuthenticationSessionProvider.createRootAuthenticationSession(InfinispanAuthenticationSessionProvider.java:8
2)
        at org.keycloak.services.managers.AuthenticationManager.createOrJoinLogoutSession(AuthenticationManager.java:289)
        at org.keycloak.services.managers.AuthenticationManager.browserLogout(AuthenticationManager.java:524)
        at org.keycloak.protocol.oidc.endpoints.LogoutEndpoint.initiateBrowserLogout(LogoutEndpoint.java:255)
        at org.keycloak.protocol.oidc.endpoints.LogoutEndpoint.logout(LogoutEndpoint.java:144)
        at sun.reflect.GeneratedMethodAccessor1351.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498) 

What is the issue?