Swiper two fingers mobile spazz

I am trying to disable any multi touch from the body using event handler but it’s not working.
On ios safari and webview when I touch the swiper with two fingers the screen flickers between the sliders, very unpleasant :frowning:

https://www.w3schools.com/jsref/event_touch_touches.asp

<body is="dmx-app" class="sw-app" id="xxx" ontouchstart="touchHandler(event)" ontouchmove="touchHandler(event)">

    $(document).ready(function () {
        //Disabale multi touch spazz from swiper
        function touchHandler(event) {
            if (event.touches.length > 1) {
                //the event is multi-touch
                //you can then prevent the behavior
                event.preventDefault()
            }
        }
    });

Any ideas how to make this work?