Poster doesn't show on Safari

[indexofrefraction]

While the poster shows perfectly on Firefox and Edge (MacOS)
It does NOT show on Safari (17.4.1),
there is a flicker and then the 1st frame is shown instead.

<video class="cell-video" title="Test" 
    data-ratio="4:3" 
    data-download="Test720.mp4" 
    data-poster="Test720.jpg" 
    data-src="Test720.mp4,Test720.webm" 
    data-type="video/mp4,video/webm" 
    data-size="360,360" 
    data-fit="fill">
</video>

this is not optimal for videos which don't have a good 1st frame
(eg black frame) and you want a meaningful preview.

.plyr__poster { z-index: 3; }
.plyr__control  { z-index: 4; }

these css changes first seemed to fix the problem,
but then you can't cue after start