PointHandler intermittently reports incorrect pressure values

I've found this strange behaviour using `PointHandler`. With the following code:

import QtQuick
import QtQuick.Window

Window {
    id: appWindow
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

    PointHandler{
        onPointChanged: console.debug(pressure)
    }
}

Testing this code with a stylus, the pressure value intermittently switches between 1.0 and other (correct) values. So for example the output of the code above looks like this:

0.54296875

1

0.5478515625

1

0.552734375

1

and so on.
I've reproduced this on Windows and Linux (using Lenovo Yoga 920 and Hp Envy x360).