NestedSet not moving children of child nodes correctly

<?php

$root = new Test();
$root->name = '1';
$root->save();

// Create root node
$tree = Doctrine::getTable('Test')->getTree();
$tree->createRoot($root);

// Create child node
$child1 = new Test();
$child1->name = '2';
$child1->save();

// Add child
$child1->getNode()->moveAsLastChildOf($root);

// Create child node
$child2 = new Test();
$child2->name = '3';
$child2->save();

// Add child2 as node of child1
$child2->getNode()->moveAsLastChildOf($child1);

// Create child node
$child3 = new Test();
$child3->name = '4';
$child3->save();

// Add child3 as node of child2
$child3->getNode()->moveAsLastChildOf($child2);

// Add another root just to be nice
$root2 = new Test();
$root2->name = '5';
$root2->save();

// Create root node
$tree->createRoot($root2);

/**
 * Now we have the following tree (Each '-' indicates 1 level):
 * 1
 * - 2
 * - - 3
 * - - - 4
 * 5
 */

/**
 * Lets say I want to move node '3' to be a root.
 * With this I assume that all of the current nodes
 * children will be moved with it:
 */
$tree->createRoot(child2);

/**
 * Now the (implied) tree should look like this:
 * 1
 * - 2
 * 3
 * - 4
 * 5
 * 
 * Instead, the tree actually looks like this:
 * 1
 * - 2
 * - - - 4
 * 3
 * 5
 */

/**
 * I will now demostrate incorrect moving back of child nodes.
 */
$child2->getNode()->moveAsLastChildOf($child1);
/**
 * Now the tree should go back to looking like this:
 * 1
 * - 2
 * - - 3
 * - - - 4
 * 5
 * 
 * But the tree now looks like this:
 * 1
 * - 2
 * - - - 4
 * - - 3
 * 5
 */