When a password is changed on backend AD, it is not synced to into POA.
Every time a password is changed, event:
Password synchronization for user "<USERNAME>" (RID: 1234) failed: [Connect to '<HOSTNAME>' server] RPC service unavailable. (Error code: 0x800706ba).
Is registered on ADSyncAgent server residing in customer's AD.
Password filter, the service which detects password changes is unable to retrieve the password due to RPC service unavailability on
Please ensure that customer's servers are configured in accordance with CDI User guide, page 9 - Firewall rules.