So this is probably an easy fix.
And if I understand what you want then,
1, place the wired headphone animations on it's own Timeline.
2, Add another enter viewport trigger element like a rectangle across the scene. In the example below I have one that shows up as a red line. But for the real one you can set it to no colour and no border so it is not seen.
3, The Enter viewport should be set to continue the wired timeline.
Using continue will not 'Start' the timeline the next time you scroll the trigger into view because we are on continue and there is nothing else on the timeline to continue to.
Having the wire animation on it's own timeline also frees you up on over complicating the Main Timeline.
Upload Responsive Test_MHv1.hype.zip (363.3 KB)
p.s, I meant post a zipped copy of the actual Hype doc, like the one I have posted. Instead of an exported one.