Resume timeline upon resume slide

Here's what I (sort of) know based on what I've read over the years in previous discussions. 

Some folks have asked about a user exiting the course partway through a video. The video always restarts when the user returns. That's been called expected behavior. Yet a video will resume where it left off if the user goes to another slide and returns to the slide with the video. So "Resume saved state" does resume the timeline from its most recent point as long as the user stays in the course.

I've also read that what happens on the last slide the user visits doesn't get saved. It has been mentioned that the data needed to resume a slide is only sent to the LMS when the user moves to another slide. So if the user exits the course, that resume data for the slide they return to can't be retrieved, because it was never stored.

I don't know if that's LMS dependent or not. And I can't say how any of this might have changed with Storyline updates. 

It is why some folks use a custom EXIT tab/button. It doesn't run the Exit Course trigger. Instead, it jumps to a "confirm exit" slide that is unconnected from the rest of the course. That slide has to buttons: one to exit the course and one that jump back to the previous slide. That ensures the resume data from the "last" slide visited has been saved (assuming, of course, that the user clicks the EXIT tab/button instead of just closing the browser).