NDB Binlog: Node: 4, down, Subscriber bitmask 0 (1 reply)

Our application was not able to handle transactions all of a sudden with a Heuristic Exception.
Caused by: com.atomikos.icatch.HeurMixedException: Heuristic Exception
at com.atomikos.icatch.imp.CoordinatorStateHandler.commit(CoordinatorStateHandler.java:601)
at com.atomikos.icatch.imp.IndoubtStateHandler.commit(IndoubtStateHandler.java:184)
at com.atomikos.icatch.imp.CoordinatorImp.commit(CoordinatorImp.java:715)
at com.atomikos.icatch.imp.CoordinatorImp.terminate(CoordinatorImp.java:975)
at com.atomikos.icatch.imp.CompositeTerminatorImp.commit(CompositeTerminatorImp.java:82)
at com.atomikos.icatch.imp.CompositeTransactionImp.commit(CompositeTransactionImp.java:336)
at com.atomikos.icatch.jta.TransactionImp.commit(TransactionImp.java:208)
... 62 more

From NDB log below, it showed that NDB Binlog Node 4 was down at 22:05:07.
2014-08-30 22:05:07 3786 [Note] NDB Binlog: Node: 4, down, Subscriber bitmask 00

However in the NDB Manager Client, it showed all the nodes were up and running. After a restart of the NDB cluster though the application was able to write to the database. Does anyone have a clue what was going on? Thanks in advance.