Sifting through event log messages and am unable to find any troubleshooting information to assist with this Event:

Unable to communicate with the Microsoft Exchange Information Store service to coordinate log truncation for database 'MB\SERVER-03' due to an RPC communication failure. Error: 1722
Extended error: Failed to open a log truncation context to source server 'SERVER-01.DOMAIN.COM'. Hresult: 0x6ba. Error: An unexpected error occurred. Error (0x6ba).

This is a 3 server Exchange2013 DAG group, all servers running v15 build 1104.5.

If I run the Get-MailboxDatabaseCopyStatus on the source server it shows that the specified Mailbox database copy is healthy.

Any suggestions on how I could further troubleshoot this event?

Hi,

According to the error message, it seems that something wrong with RPC connection between 'SERVER-01.DOMAIN.COM' and SERVER-03 when communicate with Exchange Information Store service.

Do you get this error on your all Exchange server? Do you have modify the network settings before this issue arise?

This issue's related to network problem, ensure the firewall allow RPC calls.

Allen,

The errors are abundant on one server post CU9 update. A 2nd server only has one entry listed which was on the day of the CU9 update. The 3rd server has no such event entries. Network settings had not been modified pre or post CU9 update, they were logged by the event system during/post CU9. No firewall settings were changed that would prevent communication between Exchange servers.