So you need to analyze what's different when you revisit the project vs the first time.
Are you skipping over the slide (or master) that has the trigger that loads the widget?
Is there another (unrelated) JavaScript trigger that breaks everything else?
Are you resuming the course (vs restarting) and so the session inherits the original row number for this user?
You can always open the developer console and then refresh the page. As you go, see if there are any errors - it's usually some stray JavaScript that you either didn't know or forgot about that breaks things.
If you can't find anything, feel free to send us the story file via the
Custom Development portal, we'll check as well. Note that we don't need your entire project, just those slides that deal with the sheets operations.