How to preserve link relationships when copy-pasting groups of slides in Keynote

Hello, I've been creating some interactive quizzes using Keynote and the Links Only setting. I've made several templates for various question types, as I'll be using the same question type with different content over and over again in different lessons. It takes a series of anywhere from 3 slides for a true-false question to 37 slides for each matching pairs type question, in order to encompass all the possible permutations of user interaction with the material.

My problem is that I still don't understand why, after I've created all the appropriate links for jumping back and forth between slides during the quiz, sometimes if I go to copy that sequence and place it into another file or another part of the same file, sometimes the link relationships between slides are preserved and sometimes they disappear, or it'll just say "there is no link for this slide".

I've learned that you can't copy and delete the slide series before pasting it, or the links will be deleted too. I've also learned that you have to copy-paste all the relevant slides at the same time.

But sometimes, even when I copy the slide series without deleting it, and go to paste it into another file, it only keeps the Next Slide links and deletes all the others. Then later I'll think I'm doing the exact same thing, and happily the slide links are maintained with the appropriate numbers. For example, if slide 55 of my template has a link that says to jump to slide 58, when it's copy-pasted it could be slide 10 linking to slide 13, which is exactly what I want. But other times I think I'm doing the same thing, and the link is just gone. Or it'll continue to point to slide 58.

Any pointers? It would save me a boat-load of work to get this figured out.