group height changed with item.top when navigate the timeline even set the heightmode with fixed

[Haiyang2017]

set the groupHeightMode to fixed,
when navigate the timeline，the item.top will be changed and then the group height will be changed.
any solution? thx very much.

i can't run timeline in jsfiddle.
so i remake the problem in https://jshare.com.cn/temp/FptwxQ

pay attention to the "two group".

I guess, maybe sth wrong with the _calculateHeight code, because the item.top change frequently and then the group height changed. I'm not sure.

key: '_calculateHeight',
value: function _calculateHeight(margin) {
  // recalculate the height of the group
  var height = void 0;
 
  var items = void 0;

  if (this.heightMode === 'fixed') {
    items = util.toArray(this.items);
  } else {
    // default or 'auto'
    items = this.visibleItems;
  }

  if (items.length > 0) {
    var min = items[0].top;
    var max = items[0].top + items[0].height;
    util.forEach(items, function (item) {
      min = Math.min(min, item.top);
      max = Math.max(max, item.top + item.height);
    });
    if (min > margin.axis) {
      // there is an empty gap between the lowest item and the axis
      var offset = min - margin.axis;
      max -= offset;
      util.forEach(items, function (item) {
        item.top -= offset;
      });
    }
    height = max + margin.item.vertical / 2;
  } else {
    height = 0;
  }
  height = Math.max(height, this.props.label.height);

  return height;
}

specially

if (min > margin.axis) {
// there is an empty gap between the lowest item and the axis
var offset = min - margin.axis;
max -= offset;
util.forEach(items, function (item) {
item.top -= offset;
});