Thank you for the reply! I did end up implementing it this way and it works. I’m still a bit new to UE and so this was a good push to get me thinking in terms of interfaces.
However, want to also add for those who find this post in the future, I think the original issue in my logic was one that could be solved without interfaces (in case someone doesn’t want to use that method for whatever reason).
Namely, I was trying to use the “Montage Set Next Section” on a basic reference to the montage from data, when what I needed to be doing was getting a ref to the currently playing instance of my montage using Get Current Montage, as shown in @illspiritx 's solution.