The latest update (before today) was chapter 4. You could NOT have played chapter 4 on an old save. If you’re having this issue now, you would have had it then. Nothing has changed in the code between chapter 4 and today’s update. The issue described above is due to trying to play an old save made before the chapter 4 update. I explained it in 3 different devlogs:
https://firfireweed.itch.io/cantata/devlog/1081452/cantata-chapter-4-is-live