DESCRIPTION: SSPI handshake failed with error code 0x8009030c, state 14 while establishing a connection with integrated security; the connection has been closed. Reason: AcceptSecurityContext failed. The Windows error code indicates the cause of failure. [CLIENT: 10.12.23.345].
This can be related to an AD login account expiring and the user leaving SSMS or something running on their PC. The account eventually locks out and SQL sees this message until the user resets their password.