I had received below error in Analysis Services Process task.
Internal error: The operation terminated unsuccessfully.
Initially I did not understand where was the problem since it runs successfully when we run this package through SQL Server Agent Job which does run under DBA group account. But one of our DBA execute this package under his authentication and this error occured. So I asked DBA to create a SQL Server Agent Job and execute this package from newly created job and it worked.
For more information on this issue. Please refer to below URL.
Hope it would help you.