MultiPointTouchArea first touch point jumps around

import QtQuick 2.15

Item {
  width: 600
  height: 600

  MultiPointTouchArea {
    anchors.fill: parent
    mouseEnabled: false
    minimumTouchPoints: 1
    maximumTouchPoints: 2
    touchPoints: [
      TouchPoint { id: point1 },
      TouchPoint { id: point2 }
    ]

    Rectangle {
      x: point1.x - width / 2
      y: point1.y - height / 2
      width: 100; height: width; radius: width
      color: '#80ff0000'
    }
    Rectangle {
      x: point1.previousX - width / 2
      y: point1.previousY - height / 2
      width: 80; height: width; radius: width
      color: '#80ffff00'
    }
    Rectangle {
      x: point1.sceneX - width / 2
      y: point1.sceneY - height / 2
      width: 60; height: width; radius: width
      color: '#800000ff'
    }
    Rectangle {
      x: point1.startX - width / 2
      y: point1.startY - height / 2
      width: 80; height: width; radius: width
      color: '#80000000'
    }
    Rectangle {
      x: point2.x - width / 2
      y: point2.y - height / 2
      width: 100; height: width; radius: width
      color: 'green'
    }
  }
}