Consider the following scenario:
You use the AlwaysOn Availability Groups feature in Microsoft SQL Server 2014 SP1 or SP2.
You enable SQL Server Managed Backup on a database that belongs to an availability group.
You connect to an availability replica that's not the preferred backup replica.
You use the smart_admin.sp_backup_on_demand stored procedure to create a database backup.
In this scenario, the database backup isn't created successfully.
The issue was first fixed in the following cumulative update of SQL Server:
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. We recommend that you download and install the latest cumulative updates for SQL Server:
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.