Copy custom field values using Built In Scripts is not working

Question

I created a Filter to list down the issues in which I want to copy the values from a Issue Picker Custom Field Type to Multiple Issue Picker (created via Script Runner).

Built In scripts --> Copy custom field values

On preview, I am able to view this message:

Will operate on 2 issue(s) from the Copy Custom Fields filter....
Copying source field JIRA Project Mapping to target field Jira Project Issue Picker.

But on Run:

0 issue(s) modified.

Mark Northcott_clxwl6 · Answer

I am trying to copy data from one custom field to another and both are Text Field (multi-line). If I do a filter of the issues in the project I see 88 issues with content in the field but only 4 had their data copied using the ScriptRunner. Another had 352 possible but only 55 were copied. 
I've noticed that the ones that were copied were at the top of the list sorted by updated date. Those that were copied had an update date of 10 June 2023 and later.

So it seems that the update date determines when the fields are copied.

Ty Taylor · Answer

I have the same issue. I have 2 identical Text Field (single line) fields.

Preview Returns:

Will operate on 407 issue(s) from the All MY Issues filter....
Copying source field External issue 1 to target field External issue ID.

Clicking on "Run" returns: 0 issue(s) modified.

The values are never copied over.

SK_xpcoo4 · Answer

We are seeing "0 issue(s) modified" even when the data type is identical (number field).
Edit: Nevermind, CF scope issue.