How to clear collections in javafx.scene.Scene$MouseHandler?

I have got 2 Pane. The first pane is main menu, there is only Rectangle in its children. The second pane is my game. When I go to main menu I use following method to clear game pane

//Fighting fighting = new Fighting();
//There is Pane fighting in fighting
if(fighting != null) {
    fighting.getFighting().getChildren().clear();
    fighting = null;
    System.gc();
}

When I scene.setRoot(fighting.getFighting()); and don't do anything(don't hover on objects which has OnMouse...(), don't call methods which move player) and exit to main menu(by clicking Esc)

scene.setOnKeyPressed(event -> {
    if (event.getCode()==KeyCode.ENTER) setFighting();
    if (event.getCode()==KeyCode.ESCAPE) setMainMenu();
});

In such case I don't have problems with memory and GC deletes useless objects.

But if I click/hover on any objects with listeners or call move() on player, GC won't delete the same object. And if I re-enter game pane and use it normally, GC will delete objects from prevoius session and won't delete them from current session

In my profiler I've found out that references on these useless objects are stored in Pane which is in one of ArrayLists in anonymous class MouseHandler in Scene. Can't add image good.

Also I've found out that there are only 2 Pane in heap. One of them is mainMenu. I've understood it because there is only Rectangle in its children. And the second's pane's children equals children.size() == 0.

It's code from Scene & MouseHandler

private MouseHandler mouseHandler;

class MouseHandler {

   /* lists needed for enter/exit events generation */
    private final List<EventTarget> pdrEventTargets = new ArrayList<EventTarget>();
    private final List<EventTarget> currentEventTargets = new ArrayList<EventTarget>();
    private final List<EventTarget> newEventTargets = new ArrayList<EventTarget>();

    private final List<EventTarget> fullPDRCurrentEventTargets = new ArrayList<EventTarget>();
    private final List<EventTarget> fullPDRNewEventTargets = new ArrayList<EventTarget>();
    private EventTarget fullPDRCurrentTarget = null;

}

Is it possible to clear these collections or to fix memory leak? Thanks for answers