I just checking our Unity server and I saw lot of this warning error message in our Unity server.
We have Unity 5.0 with CUCM 6.1
Event ID 1017
The Cisco Unity service that monitors Active Directory (AvDSAD) is skipping a synchronization cycle because it failed to connect to domain controller XXXX.ad.XXXX.com. Ensure that the server is accessible and is configured as a domain controller, and that no DNS issues exist. The service has failed to connect to this domain controller for 11 consecutive synchronization cycle(s). After 15 consecutive failed connection(s), The Cisco Unity service that monitors Active Directory (AvDSAD) will attempt to connect to a different domain controller.
To get rid of the current incorrect DC and/or GC, you just uncheck the "Enable automatic server search functionality on reconnects..." toward the bottom of both the DC and GC tabs and fill the correct DC and GC in manually where you have the two blanks. Once you do this, click Save and then click Force Reconnect. This should cause Unity to reconnect with the manual DC and GC. When it completes syncing with each server, it will fill in and replace the current incorrect one.