If a connection.end operation broadcasts an error for a XA JDBC connection, it could loop endlessly:
09/01/2018 14:43:16,805 WARN [com.arjuna.ats.jta] (http task-73) ARJUNA016056: TransactionImple.delistResource - caught exception during delist : XAException.XAER_RMFAIL: oracle.jdbc.xa.OracleXAException
at oracle.jdbc.xa.OracleXAResource.checkError(OracleXAResource.java:1110)
at oracle.jdbc.xa.client.OracleXAResource.end(OracleXAResource.java:436)
at org.jboss.jca.adapters.jdbc.xa.XAManagedConnection.end(XAManagedConnection.java:295)
at org.jboss.jca.core.tx.jbossts.XAResourceWrapperImpl.end(XAResourceWrapperImpl.java:118)
at org.jboss.jca.core.tx.jbossts.XAResourceWrapperStatImpl.end(XAResourceWrapperStatImpl.java:96)
at com.arjuna.ats.internal.jta.transaction.arjunacore.TransactionImple.delistResource(TransactionImple.java:914)
at org.jboss.jca.core.connectionmanager.listener.TxConnectionListener.haltCatchFire(TxConnectionListener.java:768)
at org.jboss.jca.core.connectionmanager.listener.AbstractConnectionListener.connectionErrorOccurred(AbstractConnectionListener.java:468)
at org.jboss.jca.adapters.jdbc.BaseWrapperManagedConnection.broadcastConnectionError(BaseWrapperManagedConnection.java:673)
at org.jboss.jca.adapters.jdbc.xa.XAManagedConnection.end(XAManagedConnection.java:301)
at org.jboss.jca.core.tx.jbossts.XAResourceWrapperImpl.end(XAResourceWrapperImpl.java:118)
at org.jboss.jca.core.tx.jbossts.XAResourceWrapperStatImpl.end(XAResourceWrapperStatImpl.java:96)
at com.arjuna.ats.internal.jta.transaction.arjunacore.TransactionImple.delistResource(TransactionImple.java:914)
at org.jboss.jca.core.connectionmanager.listener.TxConnectionListener.haltCatchFire(TxConnectionListener.java:768)
at org.jboss.jca.core.connectionmanager.listener.AbstractConnectionListener.connectionErrorOccurred(AbstractConnectionListener.java:468)
at org.jboss.jca.adapters.jdbc.BaseWrapperManagedConnection.broadcastConnectionError(BaseWrapperManagedConnection.java:673)
....
REPEAT ENDLESSLY
....
at org.jboss.jca.adapters.jdbc.xa.XAManagedConnection.end(XAManagedConnection.java:301)
at org.jboss.jca.core.tx.jbossts.XAResourceWrapperImpl.end(XAResourceWrapperImpl.java:118)
at org.jboss.jca.core.tx.jbossts.XAResourceWrapperStatImpl.end(XAResourceWrapperStatImpl.java:96)
at com.arjuna.ats.internal.jta.transaction.arjunacore.TransactionImple.delistResource(TransactionImple.java:914)
at org.jboss.jca.core.connectionmanager.listener.TxConnectionListener.haltCatchFire(TxConnectionListener.java:768)
at org.jboss.jca.core.connectionmanager.listener.AbstractConnectionListener.connectionErrorOccurred(AbstractConnectionListener.java:468)
at org.jboss.jca.adapters.jdbc.BaseWrapperManagedConnection.broadcastConnectionError(BaseWrapperManagedConnection.java:673)
at org.jboss.jca.adapters.jdbc.xa.XAManagedConnection.end(XAManagedConnection.java:301)
at org.jboss.jca.core.tx.jbossts.XAResourceWrapperImpl.end(XAResourceWrapperImpl.java:118)
at org.jboss.jca.core.tx.jbossts.XAResourceWrapperStatImpl.end(XAResourceWrapperStatImpl.java:96)
at com.arjuna.ats.internal.jta.transaction.arjunacore.TransactionImple.delistResource(TransactionImple.java:914)
at org.jboss.jca.core.connectionmanager.listener.TxConnectionListener.haltCatchFire(TxConnectionListener.java:768)
at org.jboss.jca.core.connectionmanager.listener.AbstractConnectionListener.connectionErrorOccurred(AbstractConnectionListener.java:468)
at org.jboss.jca.adapters.jdbc.BaseWrapperManagedConnection.broadcastConnectionError(BaseWrapperManagedConnection.java:673)
at org.jboss.jca.adapters.jdbc.xa.XAManagedConnection.end(XAManagedConnection.java:301)
at org.jboss.jca.core.tx.jbossts.XAResourceWrapperImpl.end(XAResourceWrapperImpl.java:118)
at org.jboss.jca.core.tx.jbossts.XAResourceWrapperStatImpl.end(XAResourceWrapperStatImpl.java:96)
at com.arjuna.ats.internal.jta.transaction.arjunacore.TransactionImple.delistResource(TransactionImple.java:914)
at org.jboss.jca.core.connectionmanager.listener.TxConnectionListener.haltCatchFire(TxConnectionListener.java:768)
at org.jboss.jca.core.connectionmanager.listener.AbstractConnectionListener.connectionErrorOccurred(AbstractConnectionListener.java:468)
at org.jboss.jca.adapters.jdbc.BaseWrapperManagedConnection.broadcastConnectionError(BaseWrapperManagedConnection.java:673)
at org.jboss.jca.adapters.jdbc.xa.XAManagedConnection.end(XAManagedConnection.java:301)
at org.jboss.jca.core.tx.jbossts.XAResourceWrapperImpl.end(XAResourceWrapperImpl.java:118)
at org.jboss.jca.core.tx.jbossts.XAResourceWrapperStatImpl.end(XAResourceWrapperStatImpl.java:96)
at com.arjuna.ats.internal.jta.transaction.arjunacore.TransactionImple.delistResource(TransactionImple.java:914)
at org.jboss.jca.core.connectionmanager.listener.TxConnectionListener.haltCatchFire(TxConnectionListener.java:768)
at org.jboss.jca.core.connectionmanager.listener.AbstractConnectionListener.connectionErrorOccurred(AbstractConnectionListener.java:468)
at org.jboss.jca.adapters.jdbc.BaseWrapperManagedConnection.broadcastConnectionError(BaseWrapperManagedConnection.java:673)

As a result, the reentrant lock/unlock system gets out of hand the lock in the connection is not entirely unlocked.