Possible schema corruption. Run DBCC CHECKCATALOG.
Note If you use SQL Server 2014 RTM or SQL Server 2014 Cumulative Update 1 (CU1), you may receive the errors as described in the symptom section. Error 211 is generic metadata corruption, state 50 is specific to this problem that will occur only if you set INCREMENTAL=ON.
The issue was first fixed in the following cumulative update of SQL Server.
Article ID: 2970386 - Last Review: 29 Jul 2015 - Revision: 1