This bug was discovered while using getDescendants with the new toHierarchy function. Rather than containing the correct child elements in the __children field, it contains whatever the next record is. Each record only has a single child, which is the record with the next-highest lft value. You can see this in the following pastebin. Notice that the very bottom element is placed around level 15 in the tree, yet it should be level 4 according to the "level" field.
The line that was used to produce the above pastebin was:
print_r($children = $file->getNode()
The class used for $file is: http://pastebin.ca/1673706