root node does not rebalance avl tree

Question

Hello guys i'm implementing an avl tree and trying to self balance the tree but the root node does not balance. It only balances the left and right subtree. when i input 50 40 30 10, the root note should be 40 but instead it remains 50 which is wrong. Please could someone take a look at the code to what i did wrong. Thanks

Below is my code:

public void insert(T data){

    AVLNode<T> newNode = new AVLNode<T>(data);
    if(isEmpty()){
        root = newNode;
    }
    else{
        insert(root, newNode);
    }

}

private void insert(AVLNode<T> root, AVLNode<T> newNode){

 if(newNode.getData().compareTo(root.getData())<0){
        if(root.getLeftChild()!=null){
        AVLNode<T> leftNodes = root.getLeftChild();
        insert(leftNodes, newNode);
        root.setLeftChild(rebalance(leftNodes));
        }
        else{
            root.setLeftChild(newNode);
        }
    }
    else if(newNode.getData().compareTo(root.getData())>0){
        if(root.getRightChild()!=null){
        AVLNode<T> rightNodes = root.getRightChild();
        insert(rightNodes, newNode);
        root.setRightChild(rebalance(rightNodes));
    }
        else{
            root.setRightChild(newNode);
        }
    }
    else{
          root.setData(newNode.getData());
    }
    updateHeight(root); 
}

//re-balances the tree.
private AVLNode<T> rebalance(AVLNode<T> root){
    int difference = balance(root);
    if (difference > 1){
        if(balance(root.getLeftChild())>0){
            root = rotateRight(root);
        }
        else{
            root = rotateLeftRight(root);
        }
    }
    else if(difference < -1){
        if(balance(root.getRightChild())<0){
            root = rotateLeft(root);
        }
        else{
            root = rotateRightLeft(root);
        }
    }
    return root;
}

//updates the height of the tree.
public void updateHeight(AVLNode<T> root){
    if((root.getLeftChild()==null) && (root.getRightChild()!=null)){
        root.setHeight(root.getRightChild().getHeight()+1);
    }
    else if((root.getLeftChild() !=null)&&(root.getRightChild()==null)){
        root.setHeight(root.getLeftChild().getHeight()+1);
    }
    else
        root.setHeight(Math.max(getHeight(root.getLeftChild()), getHeight(root.getRightChild()))+1);
}

private int balance(AVLNode<T> root) {
    return getHeight(root.getLeftChild())-getHeight(root.getRightChild());
}

//single left left rotation of the tree
private AVLNode<T> rotateLeft(AVLNode<T> root){
    AVLNode<T> NodeA = root.getRightChild();
    root.setRightChild(NodeA.getLeftChild());
    NodeA.setLeftChild(root);
    root.setHeight(Math.max(getHeight(root.getLeftChild()), getHeight(root.getRightChild()))+1); //updates the height
    NodeA.setHeight(Math.max(getHeight(NodeA.getLeftChild()), getHeight(NodeA.getRightChild()))+1);
    return NodeA;
}
//single right right rotation of the tree
private AVLNode<T> rotateRight(AVLNode<T> root){
    AVLNode<T> NodeA = root.getLeftChild();
    root.setLeftChild(NodeA.getRightChild());
    NodeA.setRightChild(root);
    root.setHeight(Math.max(getHeight(root.getLeftChild()), getHeight(root.getRightChild()))+1); //updates the height of the AVL tree
    NodeA.setHeight(Math.max(getHeight(NodeA.getLeftChild()), getHeight(NodeA.getRightChild()))+1);
    return NodeA;
}
//a double rotation. Left right rotation
private AVLNode<T> rotateLeftRight(AVLNode<T> root){
    AVLNode<T> nodeA = root.getLeftChild();
    root.setLeftChild(rotateLeft(nodeA));
    return rotateRight(root);
}
//a right left rotation
private AVLNode<T> rotateRightLeft(AVLNode<T> root){
    AVLNode<T> nodeA = root.getRightChild();
    root.setRightChild(rotateRight(nodeA));
    return rotateLeft(root);
}