Can clicking too fast cause a trigger to not be set?

Best guess: Some folks are getting through at least one section without the associated variable being adjusted to True. 

For example, that could happen if the variable is adjusted when the last slide's timeline ends, but the user can leave the slide before the that happens. If that could be the problem, the solution is to use a "when" in triggers that adjust the variables to True that will always happen before the user can return to the menu slide. 

If that can't be the problem, well, further troubleshooting is just more guessing without seeing the .story file. If you upload it, someone might be able to solve the issue.

Here are the best practices for uploading a .story file: 

• Only include slides that are related to the problem.
• Be sure objects, layers, motion paths, and variables have meaningful names.
• If there is proprietary content, replace or delete it. For example, replace proprietary text with “ipsum lorem” text.

Here's what I noticed in your file:

• All of the parts adjust the associated variable to True on the first slide of the scene—except for the North American Indigenous scene. That variable isn't adjusted to True until the last slide in the scene. 
• The slides include the PREV button. That means I can jump right back to the menu slide from the first slide of each scene.
• When I do that, all of the variables are True—except the Indigenous variable. 

Thus, it seems likely that some folks can never advance from the menu slide because they didn't step through all of the slides, the Indigenous variable remains False, and the Next button on the menu slide is never enabled.

The easiest solution: Remove the PREV button from the first slide in each scene. That will prevent the user from returning to the menu without completing the scene.

P.S. Kudos for having an object set up to show all of the variables. Those are very handy for troubleshooting. 👍

Thank you. That makes sense. Imagine users not following directions :P :P