If you define 700 columns, then the horizontal lines are missing:
for (int i = 0; i < 700; i++)
{
      var nameCol = new GridViewDataColumn() { DataMemberBinding = new Binding("Name") };
      this.radTreeListView.Columns.Add(nameCol);
}

Refreshing CollectionViewSource bound to TreeListView results in wrong display rendering

When alternation is applied, some rows get expended/collapsed when other rows are actually expanded/collapsed.