navigator.getUserMedia is now deprecated and is replaced by navigator.mediaDevices.getUserMedia. To fix this bug replace all versions of navigator.getUserMedia with navigator.mediaDevices.getUserMedia
The video eventListener for play fires up too early on low-end machines, before the video is fully loaded, which causes errors to pop up from the Face API and terminates the script (tested on Debian [Firefox] and Windows [Chrome, Firefox]). Replaced by playing event, which fires up when the media has enough data to start playing.