Maybe your SIP traversal zone is down or as SIP fails with the 407 it tries to interwork the call.
Did you check the Traversal zone and how the exact search details look like?
Could you describe your deployment a bit more. Like:
How does your deployment look like?
How are your authentication settings for the different zones?
Could you explain "TMS 14.1.1 LDAP Auth"
Is only the VCS-C running the provisioning server or also the VCS-E?
Is the sip domain also added to the VCS-E