Метод stop()

<videotronic-player
    id="my-player"
    data-video-src = "https://cdn.videotronic.io/assets/video/example-720.mp4"
    data-video-poster = "https://cdn.videotronic.io/assets/img/poster.png"
    data-video-controls
></videotronic-player>

<button id="my-player-btn" type="button" >Остановить</button>

<script>
    {
        const player = document.getElementById('my-player');
        const btn = document.getElementById('my-player-btn');

        //
        (window.videotronic = window.videotronic || {cmd:[]}).cmd.push(()=>{
            btn.addEventListener('click', ()=>{
                player.stop();
            })
        });
    }
</script>