You create a distributed availability group in Microsoft SQL Server 2016 and then install the cumulative update 1 (CU1) for SQL Server 2016. However, when you query the DMV sys.dm_hadr_availability_replica_states primary replica of the primary availability group, incorrect result is returned. Specifically, the value in the synchronization_health column doesn't match the value in the synchronization_health_desc column. For example, if the value in the synchronization_health column returns 2, the value in the synchronization_health_desc column may return NOT_HEALTHY.
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server:
Latest cumulative update for SQL Server 2016
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Learn about the terminologythat Microsoft uses to describe software updates.