Symptoms
Assume that you use Microsoft SQL Server 2012 Reporting Services (SSRS 2012) Service Pack 1 (SP1) Cumulative Update 8 (CU8) or a later version. When you build a matrix with text box and use the Lookup function in its expression, duplicate records occur in the report rendering.
Resolution
The issue was first fixed in the following cumulative update of SQL Server.
Cumulative Update 1 for SQL Server 2014 SP1 /en-us/help/3067839
Cumulative Update 6 for SQL Server 2014 /en-us/help/3031047
Cumulative Update 3 for SQL Server 2012 SP2 /en-us/help/3002049
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:
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
