Error message when trying to copy a scene or slide?

I've recently been working on a project in Storyline and it's designed so the learner may have the option of audio (narration) only, text only or audio and text. Naturally this means that from the introductory slide there has to be at least two branches to the slides to correlate with the options. However, everytime I try to copy a slide or a whole scene, an error message arises saying something went wrong, despite the fact that if I copy the very first slide, that one particular slide will work. The only hypothetical I have so far is that the slide that does copy has an arrow directly down the middle (in story view) to the next slide whereas the ones that won't, have either two arrows or a single arrow placed on the right to the next slide.

Could anybody offer any insight? Need help!

Many thanks!