Audio not playing on Mac, Safari version 12.0.3

I'm wondering if this is the same issue i'm having, although it sounds slightly different.  I am not experiencing it in Safari 11.1 but I just screenshared with a coworker who showed me that in safari 12.1, if he immediately clicks the "next" button to go to the next slide, the audio plays fine, so long as he didn't wait.

On any slide of the course, if he waited, say, 30 seconds to click the next button to advance to the next slide, after the slide he was on had reached the end.... the slide played, but no audio.   If he clicked "prev" and then "next" again in succession, the audio was there.

But any time that he waited a minute before clicking next to go to the next slide... the next slide plays with no audio.

I use Storyline 3 Update 6 3.6.18...