Problem with paused timeline starting when flicking back and forth between slides

I wonder if any of you good people can help? I'm working on a project that involves a number of animated flowcharts that use zooms on the base layer to zoom in to the detail whilst they are being animated on layers (they will also be narrated when complete). I pause the timeline on the base layer after a 'Start' button animates and only resume the timeline once the learner clicks 'Start' to indicate that they are ready to begin.

My issue is that, after completing the first flowchart, they are taken to the next slide, which works in the same manner. However, if the user decides to revisit the previous slide and then come back to the second flowchart, it suddenly starts the zoom on the base layer before the user has clicked 'Start'. It does the same thing if you revisit the previous slide from the first flowchart before clicking 'start'.

My slides are deliberately set to 'resume saved state' as when they revisit a slide I want them to see a layer with the final flowchart on it and they must click a button if they wish to replay it in full. I don't want to force them to sit through the full animation every time they revisit!

Maybe I am overthinking it as most users probably won't skip back a slide, but I would really like to find a solution to this!

I've de-personalised the content and added a story file with 2 flowcharts and 1 slide either side.

TIA!