"Adjust variable" trigger not working when set to Next button

Hello,

I have a set of variables to indicate when a section is finished (e.g. IntroductionComplete). They are true/false. They are used to check users have looked at every section and to check off completed sections in the menu.

If I set the variables to adjust at the "start of timeline" for the beginning of the last slide of a section, everything works as intended.

Ideally however, I would like the variable values to change when the user clicks the Next button for the last slide of the relevant section, as this is much cleaner and more accurate. Unfortunately, this does not work, and I cannot see why (I am using both the default Next button and one we've created, both have the below trigger, neither of which works).

The trigger I am using is:

      "Set IntroductionComplete to true

        When the user clicks the next button"

The only thing I can possibly see causing this is if because the slide is "finished" they aren't triggering, but if that is the case, why does clicking them work (takes you to the correct slide) but the variable doesn't change?

(Slide advance is set to by User).

Thanks in anticipation,

Kita