JavaFX duplicated children added at remove

I have a quite strange problem in javafx. If I add some rectangles to a anchorpane and delete them afterwards, I get the following exception:

java.lang.IllegalArgumentException: Children: duplicate children added: parent = AnchorPane

But now the real problem shows up: The exception is quite random. So, I do not get the exception always when I delete a rectangle and that is what I do not understand. I already debugged everything, but there are no differences between a "no exception termination" and a "with exception termination" (I hope somebody can understand my weird writing xd) Another problem is that I do not know how to reproduce this issue. It is to 100% my fault, but I cannot say what I am doing wrong.

Now my last try is to ask a question here. Does anybody has some tips for this exception? (I am using the newest IntelliJ version and JDK17 + JavaFX 17)

Rectangle/Node Class:

import javafx.beans.property.SimpleStringProperty;
import javafx.scene.shape.Rectangle;
import java.text.DecimalFormat;
import java.util.Objects;

public class MyNode extends Rectangle {

    private int myNodeId;
    private SimpleStringProperty myNodeIdProperty;
    private DecimalFormat threeDigits;

    public MyNode() {

    }

    public MyNode(double xCord, double yCord, double width, double height, int myNodeId) {
        super(xCord, yCord, width, height);

        this.myNodeId = myNodeId;

        threeDigits = new DecimalFormat("000");

        this.myNodeIdProperty = new SimpleStringProperty();
        this.myNodeIdProperty.set(threeDigits.format(myNodeId));
    }

    public int getMyNodeId() {
        return myNodeId;
    }

    public void setMyNodeId(int myNodeId) {
        this.myNodeIdProperty.set(threeDigits.format(myNodeId));
        this.myNodeId = myNodeId;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        MyNode myNode = (MyNode) o;
        return myNodeId == myNode.myNodeId;
    }

    @Override
    public int hashCode() {
        return Objects.hash(myNodeId);
    }
}

Maybe someone sees already a weird thing in my node class. As you can see, I have a unique id and a property to bind this id to a tableview cell. I add and remove the nodes with the following code:

anchorPane.getChildren().add(myNode);
anchorPane.getChildren().remove(myNode);

I see forward to your answers. Thanks.

The problem was the overrides of the equals and hashcode methods... I removed them and now everything works fine. Thank you @Slaw.