Can't remove CandlestickSet from CandlestickSeries

I continued playing with CandlestickSeries and today I was able to insert a CandlestickSet, but was unable to remove it. See "Insert" and "Delete" buttons in the code below:

ColumnLayout
{
    spacing: 5
    anchors.fill: parent

    ChartView {
        id: cv
        title: "Candlestick series"
        theme: ChartView.ChartThemeLight
        legend.alignment: Qt.AlignBottom
        antialiasing: true
        Layout.fillWidth: true
        Layout.fillHeight: true

        CandlestickSeries {
            id: series
            name: "Acme Ltd."
            increasingColor: "green"
            decreasingColor: "red"

            CandlestickSet { timestamp: 1435708800000; open: 6.90; high: 6.94; low: 5.99; close: 6.60 }
            //CandlestickSet { timestamp: 1435795200000; open: 6.69; high: 6.69; low: 6.69; close: 6.69 }
            CandlestickSet { timestamp: 1436140800000; open: 4.85; high: 6.23; low: 4.85; close: 6.00 }
            CandlestickSet { timestamp: 1436227200000; open: 5.89; high: 6.15; low: 3.77; close: 5.69 }
            //CandlestickSet { timestamp: 1436313600000; open: 4.64; high: 4.64; low: 2.54; close: 2.54 }
        }
    }

    RowLayout
    {
        Layout.margins: 10
        spacing: 5

        Button
        {
            text: "Change 2"
            onClicked: series.at(2).open = 3
        }

        Button
        {
            text: "Change 4"
            onClicked: series.at(4).open = 3
        }

        Button
        {
            text: "Insert"
            onClicked: {
                var set = Qt.createQmlObject('import QtCharts 2.2; CandlestickSet {}', series, "dynamicSnippet1");
                set.timestamp = 1435795200000
                set.open = 5.69
                set.high = 6.69
                set.low = 3.54
                set.close = 4.54
                var ret = series.insert(1, set)
                console.log("ret=", ret, set)
            }
        }

        Button
        {
            text: "Add"
            onClicked: {
                var set = Qt.createQmlObject('import QtCharts 2.2; CandlestickSet {}', series, "dynamicSnippet1");
                set.timestamp = 1436313600000 //1436413600000
                set.open = 4.64
                set.high = 4.64
                set.low = 2.54
                set.close = 2.54
                var ret = series.append(set)
                console.log("ret=", ret, set)
            }
        }

        Button
        {
            text: "Delete"
            onClicked: {
                var set = series.at(1)
                var ret = series.remove(set)
                console.log("ret=", ret, set)
            }
        }
    }

series.remove remove returned false and the chart did not change.

Also, as before, it is not clear how to append a candle.

My QT version is 6.2.