Menus in Storyline - Problem

Hello.

I have created 40+ Storyline presentations over the last few years. Each of these presentations has a hierarchical menu (topic, indented sub-topics, indented sub-sub-topics etc.) that appear on the left-hand side of the screen.

Up until the last few weeks, these menus functioned as expected. However, when I've opened presentations over the last few weeks - the menu has either:

• disappeared; or
• does not appear in the same format as it appeared when I last opened the presentation e.g., all slides are listed on the same level, as opposed to being in several levels (i.e., topic, sub-topic, sub-sub-topic ...). 

I don't want to reconstruct all of my menus because this will take at least 1 hour for each presentation.

Has anyone else experienced the same problem?

Is anyone aware of any changes (following at least 3 Storyline updates over the last 3 weeks) that might have impacted menus in existing Storyline presentations?

Any help would be appreciated.

Thank you.

Jon