p5js obj glitch

function preload(){
    obj = loadModel('includes/demos-data/3d/teapot.obj')
}

function setup() {
    createCanvas(windowWidth, windowHeight, WEBGL)
    // print(JSON.stringify(obj))
}

function draw() {
    clear()
    scale(-4)

    // for(let f of obj.faces){
    //  f[1] =1
    // }

    for(let v of obj.vertices){
        v.x += random(20)
    }

    // ?? how to rebuild after each change??

    // obj.buildGeometry(); // doesn't work
    model(obj)
}