On a Sharepoint 2010 farm I've found lately that the automatic Incremental Sync that runs for the User Profile Service daily, isn't properly syncing the information between AD and Sharepoint.
An example of this can be a user's photo not syncing from Sharepoint -> AD, or a disabled user not disappearing from AD -> Sharepoint.
If I go into Central Administration and manually run a Full Sync, all the issues clear up and everything is properly in sync.
I can confirm that the Incremental Sync job is running every day as Central Admin reports a last run time.
FIM reports the following error for all my users:
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> Microsoft.Office.Server.UserProfiles.UserProfileException: Exception while trying to migrate user 'domain\username' to 'domain\username'. ---> Microsoft.SharePoint.SPException: The user does not exist or is not unique. ---> System.Runtime.InteropServices.COMException (0x81020054): The user does not exist or is not unique.
Has anyone got any ideas on why this would be happening?