Copy a parent layer containing linked variables, ensuring that the linked variables are preserved when pasting the entire layer into another document (this issue also occurs when placing the parent layer in the library)

I need a technical title block for my work. I created a template in Illustrator, using an XML export of the variable file, and it works perfectly—EXCEPT that when I copy the title block and paste it into my document, the variables are no longer linked. (The same thing happens when I use the Illustrator library.)