WCF Kerberos SSPI error when one of the Domain Controllers is down

My WCF Service is using Windows Authentication with Kerberos, we disable the NTLM. The service is running under one Domain user account and the client on the different Domain user account. And both are configure using UPN. Both client and service are in the same domain. And the domain has two domain controllers.

The communication between the client and the service is running smoothly without any issues when both the domain controllers are online. If one of the domain controller is down, I got the following error.

A call to SSPI failed, see inner exception. ---> System.Security.Authentication.AuthenticationException: A call to SSPI failed, see inner exception. ---> System.ComponentModel.Win32Exception: The system detected a possible attempt to compromise security. Please ensure that you can contact the server that authenticated you

Please advice what should I do to eliminate this error. Thanks.