Thanks for reporting this issue and I'm sorry you're having trouble editing your story. Since this is an issue you are having only with the story builder, the best way to get assistance is to contact Esri Technical Support.
I don't have a reason to believe this would help the issue you mentioned, but one recommendation I have for your story is to use the Explorer Grid layout for your tours. The way your story is currently arranged the reader has so much scrolling to do that I don't think you can expect anyone to realistically read through the story or have an easy time finding a place they are interested in.
The guided tour layouts really should only be used when you have 10 or fewer tour places.
Owen Evans
Lead Product Engineer | StoryMaps