Lookup activity failure

I increased the query timeout as well, still it is not resolved.
Some times it is running and sometimes it is getting failed.
Researched in the web, still couldn't find the main issue.

Error : 

Operation on target Execute Fct_Transactions failed: Operation on target Lookup_New_WaterMark_Value failed: Failure happened on 'Source' side. ErrorCode=SqlOperationFailed,'Type=Microsoft.DataTransfer.Common.Shared.HybridDeliveryException,Message=A database operation failed with the following error: 'A severe error occurred on the current command. The results, if any, should be discarded.
A severe error occurred on the current command. The results, if any, should be discarded.',Source=,''Type=System.Data.SqlClient.SqlException,Message=A severe error occurred on the current command. The results, if any, should be discarded.
A severe error occurred on the current command. The results, if any, should be discarded.,Source=.Net SqlClient Data Provider,SqlErrorNumber=0,Class=11,ErrorCode=-2146232060,State=0,Errors=[{Class=11,Number=0,State=0,Message=A severe error occurred on the current command. The results, if any, should be discarded.,},{Class=20,Number=0,State=0,Message=A severe error occurred on the current command. The results, if any, should be discarded.,},],'