Help! Multi-layer tabbed timeline

Hi! I created a great looking course that uses multiple tabs that reveal various slide layers (rather than a "next" button--I wanted the background music to play throughout).

Here's the problem I'm running into: Learners can't skip back in the timeline when they're in a layer. If you click an earlier point on the timeline, nothing happens.

Another (I'm guessing related) problem, is that they can't review tabs. Once they get to the end of the narration and go to the next tab, if they click back to the previous tab it just picks up where it left off (usually just the tail end of the background music).

Any advice?

Running Storyline 2 update 4 in case it matters.