Hi Erdinc,
Could you please show us your expression in expression editor so that we can tell you what is exactly is going wrong?
In this “Add Cast/Crew to “ + GetMovieById.List.Current.Movie.Title ,
“Add Cast/Crew to “ - Static text, hence it should be always in quotes ("")
GetMovieById.List.Current.Movie.Title : Dynamic value which you are fetching from your aggregate.
Please make sure you have quotes mentioned properly in your expression.
Thanks!!