I believe it was a combo of https://jira.jboss.org/jira/browse/JBMAR-49 and https://jira.jboss.org/jira/browse/JBMAR-50.
FQN was Externalizable and NodeKey is Serializable, so the combo of them two was not working correctly. NodeKey should at least be made Externalizable anyway, shouldn't it?