Thanks for bringing this to our attention (has been this way for years with no one else reporting and hence not sure if it really affects rendering on the page). We have this fixed internally – pls expect this to be part of upcoming update.
BTW, if you need your local installation to be fixed, you can change the relevant code at line number 34 and 36 of file includes/widgets/lsow-hero-image-widget/default.php file to –
<source src="<?php echo wp_get_attachment_url($background['html5_videos']['mp4_file']); ?>"
type="video/mp4">
<source src="<?php echo wp_get_attachment_url($background['html5_videos']['ogg_file']); ?>"
type="video/ogg">
<source src="<?php echo wp_get_attachment_url($background['html5_videos']['webm_file']); ?>"
type="video/webm">