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.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.