Do you have a mix of Windows Server 2003 and Windows Server 2012 R2 domain controllers in your domain and occasionally experiencing logon issues? It could be due to Computers which changed their machine password recently and failing to communicate with domain after that. AskDS(Microsoft Active Directory support team) recently published an article about this which gives further details into this problem and a few possible workarounds. You might want to try them if you are seeing similar problems in your environment.