If you had indicated how the script is failing and what, if any error messages might be appearing, we'd have a better chance at suggestiing why it's not working and how to fix it. Simply copying a script accurately from one file to another is no guarantee that it will works correctly in the new file. The underlying layout and relationship design in the new file can keep your copied script from working.
There are a number of ways that this script might fail:
What layout is current when you run this script? Is it based on Choral_call_numbers, Performance Library, some other table occurrence?
The relationship between these occurrences could be different and thus not allow the script to work.
Your Go to related records step may be specifing a table occurrence or <Current layout> may not be a layout that works for your relationship. And this step will produce an empty found set if there are no related records via the relationship it specifies...
You perform 2 different scripts in 2 different files (Performance Library and Performance Library 2). It's not clear what these script do or if the scripts should be performed in these files.
Copy will fail if the referenced field is not on the layout that's current at the time the copy step executes.
And please note that there are better ways to pass data to a script that's to be performed (assuming that's why you copy to the clipboard), that will, unlike copy, leave any data that the user has previously copied intact.