It is the nature of the LazyContentWrapper to refetch the wrapped node again if the session has been closed. That is fine. If you then access children later it might be that the former session has been closed because it has been handled by another thread:

• thread1 creates session1
• thread1 uses LazyContentWrapper so the node is bound to session1
• thread2 creates session 2
• thread2 uses LazyContentWrapper but session1 is still open and so used
• thread2 gets a child of the node (this child node is of type DefaultContent)
• thread1 closes session1
• thread2 tries to use the child node and it fails with a session closed exception