How can we get Engage interaction to actually complete?

This may be hard to explain here --- We're asking people to complete all items in our Engage Labeled Graphic interaction before going on to the next slides. There are about 8 items plus an introduction on the Engage Interaction. Only the introduction has audio.

The behavior we're seeing is that people are listening to the entire intro, then clicking and reading all  8 items. The Next Slide button even appears. But it will not let them move on. It says they have not viewed all items on the slide. 

But they have!  If you look at the seek bar, it has stopped before it gets all the way to the end.

Any ideas of how we can get this to behave properly?  It's really making us look bad and creating a terrible usability issue.

Please advise.

Thank you,

E