Why does the Chart Type of Google Chart change?

I would like to update/modify an existing google chart’s options. Let’s say I want to with a click a button apply these options to an existing chart.

When the button “Modify Chart” is clicked, the chart options are updated (e.g. new colors are set).

What is strange is that the chart type is changed from a Combo Chart to a Line chart. Why is this happening? Even if I pass chartType: ‘ComboChart’ in the options, the chart type is still changed.

Help much appreciated.

function nuChart(d, t, a, h, x, y, st, is) {

    let obj = document.getElementById(d);
    if (obj == null) return;

    a = eval(a);

    if (a.length === 0) { return; }

    try {
        google.charts.load('current', { 'packages': ['corechart'] });
    } catch (error) {
        return;
    }

    google.charts.setOnLoadCallback(drawVisualization);

    if (a == '') { return; }

    function drawVisualization() {

        if (a === undefined) { return; }

        let data = google.visualization.arrayToDataTable(a);
        let wrapper = new google.visualization.ChartWrapper({

            chartType: t,
            dataTable: data,
            containerId: d,

            options: {
                title: h,
                vAxis: { title: y },
                hAxis: { title: x },
                seriesType: st,
                isStacked: is,
            }

        });

        wrapper.draw();

        window[d + '_wrapper'] = wrapper;

    }

}


function nuTestChart() {

    let a = [
                ['Month', 'Shane', 'Dave', 'Adam', 'Paul', 'Chris'],
                ['2019', 100, 200, 300, 400, 500],
                ['2020', 165, 238, 322, 498, 550],
                ['2021', 165, 938, 522, 998, 450],
                ['2022', 135, 1120, 599, 1268, 288]
              ];

    nuChart('google_chart', 'ComboChart', a, 'title', '', '', 'bars', false);

}

nuTestChart();

function nuModifyChart() {

  let wrapper = window["google_chart_wrapper"];

  wrapper.setOptions({
    colors: ['#e0440e', '#e6693e', '#ec8f6e', '#f3b49f', '#f6c7b6']
  });
  wrapper.draw();

}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script type="text/javascript" src="https://www.gstatic.com/charts/loader.js"></script>

<button onclick="nuModifyChart()">Modify Chart</button>

<div id="google_chart" data-nu-tab="8" data-nu-form="" class="nuHtml" data-nu-access="0" style="top: 38px; width: 450px; height: 192px; position: absolute; visibility: visible;"></div>