Material Popup is not properly anchored after being opened more than once

import QtQuick 2.15
import QtQuick.Controls 2.15
import QtQuick.Window 2.15

/*
 * Run this passing the `--style material` option to `qmlscene`.
 * The first time you open the popup, all it's OK:
 *  ______________________
 * |  __________________  |
 * | |                  | |
 * | |                  | |
 * | |                  | |
 * | |                  | |
 * | |                  | |
 * | |                  | |
 * | |                  | |
 * | |                  | |
 * |  ------------------  |
 *  ----------------------
 *
 * The second... not so well:
 *  ______________________
 * |                      |
 * |    __________________|
 * |   |                  |
 * |   |                  |
 * |   |                  |
 * |   |                  |
 * |   |                  |
 * |   |                  |
 * |   |                  |
 * |   |                  |
 * |   |                  |
 *  ----------------------
 */

Window {

    Button {
        anchors.centerIn: parent
        text: "Open popup"
        onClicked: popup.open()
    }

    Popup {
        id: popup
        anchors.centerIn: parent
        width: parent.width - 20
        height: parent.height - 20
        Button {
            anchors.centerIn: parent
            text: "Close popup"
            onClicked: popup.close()
        }
    }
}

/*
 * A workaround is set the popup's position manually. For example:
 *
 *  parent: Overlay.overlay
 *  x: Math.round((parent.width - width) / 2)
 *  y: Math.round((parent.height - height) / 2)
 *
 * I guess that is why this bug does not ocurr in a `ComboBox`
 */