How many quiz (graded) questions can a Storyline project have, per scene?

What weird behavior! The same thing happened to me when I inserted a new slide at the end of scene 2: it appeared in a 2nd column, as if it weren't linked to the previous slide. Yet, during preview, the program did progress properly from one to the other.

I think your 2.31 slide is corrupted.

• I have no idea how it got that way. You could submit a case to Articulate: Contact Support for Help with Any Articulate E-Learning Course Development Software 

There is a fix. When I delete that slide, the program will insert a new question slide within the linear "column" for that scene. So try that.