HTML5 Video Poster not working

Hey!
I am using your shortcode example for HTML5 video background:

<div class="section dark" style="height: 550px;">

	<div class="container clearfix">

		...

	</div>

	<div class="video-wrap">
		<video poster="images/videos/deskwork.jpg" preload="auto" loop autoplay muted>
			<source src='images/videos/deskwork.mp4' type='video/mp4' />
			<source src='images/videos/deskwork.webm' type='video/webm' />
		</video>
		<div class="video-overlay"></div>
	</div>

</div>

Poster image is irrelevant as it only shows when the video is loaded.

The fix that you provide here does not work: https://support.semicolonweb.com/forums/topic/video-autoplay-sliders-poster-images/

Is there any other way as this creates a bad visual user experience.

Thanks