It is a Show/Hide workflow, where you hide the group of texts and show the appropriate one. That is an older workflow but should work perfectly. I also prefer using a multistate object, because you don't have to reset the slide when revisiting which is necessary with a Show/Hide workflow.
It is not the reason that your buttons are not working, that is sure. It would have been better to use instances of one shared action (two parameters) than 15 duplicates on a slide. Not sure if that can be the reason, although I have debugged files for clients which were choking on a too big amount of duplicate advanced actions.
All buttons have their pausing point at the same location, which is fine. Since it is an advanced action, the play head will never be released.
Except possible choking (I don't know how many advanced actions you have in the full project) the only problem could be with labeling. Did you ever use the same namefor two different items, even though they are of a different type?
I am a bit worried about the labels of your decisions as well... those are not the normal generic names: Untitled1_1.... Did you get that advanced action from someone else or from a Quick Start Project? You don't seem to know the Preview button for advanced actions. Have a look at:
http://blog.lilybiri.com/advanced-actions-dialog-box-in-captivate-2017