Highcharts sankey diagram node rearrangement

Highcharts.chart('container', {
    chart: {
      width: width,
      height: height
    },
    series: [{
      keys: ['from', 'to', 'weight'],
      data: [
        ['a', 'd', 1],
        ['b', 'c', 1],
        ['c', 'd', 1]
      ],
      type: 'sankey'
    }]
  });
});

When plotting two flows, a->d and b->c->d, Highcharts gives a strange node arrangement until the page is resized or the chart is reflowed:

Actual:

Expected:

Demo: https://jsfiddle.net/applewil/ezjfarh4/6/

Why do I need to resize or reflow to get the expected arrangement?