Need some clariffications for errors

Hi All,
While running the UI Sequences individually, I am not getting any error. At the same time while I am trying to make a flowchart and run the same set of sequences together, I am facing the “UI element is not valid” error.
Note: I am not using send hot keys method, and also its a citrix based application.

Check the Selector property in the properties Pane of the Element that throws this as an error.