It’s this line
$objVideo->request->files->dash->url = preg_replace( '~sep/video/(.*?),.*?/~', 'sep/video/$1/', $objVideo->request->files->dash->url);
It happens during admin post editing, admin-ajax, and regular video-including page requests. But impossible to tell whether always, or not.
We’re streaming from Vimeo.
property is missing?
Any other debugging details needed?