angular Ui tree incrementing is duplicating

My Plunker.

In My plunker if I add some childs, then if I remove one of child record then if I add rows the rows are duplicating.

$scope.newSubItem = function(scope) {
  var nodeData = scope.$modelValue;
  nodeData.items.push({
    id: nodeData.id * 10 + nodeData.items.length,
    rowId: nodeData.rowId + '.' + (nodeData.items.length + 1),
    items: []
  });
};