Run the code:

    TreeTableView<Data> treeTableView;

    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage stage) throws Exception {
        treeTableView = new TreeTableView<Data>();
        treeTableView.setRoot(new TreeItem<Data>(new Data("Root")));
        treeTableView.getRoot().getChildren().add(new TreeItem<Data>(new Data("item 1")));
        treeTableView.getRoot().getChildren().add(new TreeItem<Data>(new Data("item 2")));
        treeTableView.getRoot().getChildren().add(new TreeItem<Data>(new Data("item 3")));
        treeTableView.getRoot().setExpanded(true);

        treeTableView.getColumns().add(new TreeTableColumn<Data, String>("Data"));
        ((TreeTableColumn<Data, String>) treeTableView.getColumns().get(0)).setCellValueFactory(new Callback<CellDataFeatures<Data, String>, ObservableValue<String>>() {
            @Override
            public ObservableValue<String> call(CellDataFeatures<Data, String> p) {
                return p.getValue().getValue().property;
            }
        });

        Button b1 = new Button("print selection");
        b1.setOnAction(new EventHandler() {
            @Override
            public void handle(Event t) {
                System.out.println("selected item : " + treeTableView.getSelectionModel().getSelectedItem());
                System.out.println("selected items : " + treeTableView.getSelectionModel().getSelectedItems());
            }
        });

        treeTableView.getSelectionModel().selectedItemProperty().addListener(new ChangeListener() {
            @Override
            public void changed(ObservableValue ov, Object t, Object t1) {
                System.out.println("Changed selection to " + t1);
            }
        });

        VBox vb = new VBox();
        vb.getChildren().addAll(b1, treeTableView);

        Scene scene = new Scene(vb, 300, 300);
        stage.setScene(scene);
        stage.show();
    }

    class Data {

        public StringProperty property;

        public Data(String data) {
            property = new SimpleStringProperty(data);
        }

        @Override
        public String toString() {
            return property.get();
        }
    }

Select "item 2".
collapse root.
Click to print selected items.

Output:
Changed selection to TreeItem [ value: item 2 ]// <- selected item.
selected item : TreeItem [ value: item 2 ] // <- after collapsing of root and clicking the button.
selected items : [null]

I expect to see droped selection and focused root.

Affected tests:
ControlsAutomatedTestSuite/javafx/scene/control/test/treetable/TreeTableAsTreeTest/multilevelJumpOnCollapsingTest