This happens whenever there is no corresponding connection listener wrapper in the cls map.

Example of the error:

05/02/2018 12:45:31,558 ERROR [org.jboss.jca.core.connectionmanager.TxConnectionManager] (http task-74) IJ000406: Throwable in returning connection: org.jboss.jca.adapters.jdbc.xa.XAManagedConnection@75c05dd6: java.lang.NullPointerException
at org.jboss.jca.core.connectionmanager.pool.mcp.SemaphoreConcurrentLinkedDequeManagedConnectionPool.returnConnection(SemaphoreConcurrentLinkedDequeManagedConnectionPool.java:731)
at org.jboss.jca.core.connectionmanager.pool.mcp.SemaphoreConcurrentLinkedDequeManagedConnectionPool.returnConnection(SemaphoreConcurrentLinkedDequeManagedConnectionPool.java:611)
at org.jboss.jca.core.connectionmanager.pool.AbstractPool.returnConnection(AbstractPool.java:849)
at org.jboss.jca.core.connectionmanager.AbstractConnectionManager.returnManagedConnection(AbstractConnectionManager.java:748)
at org.jboss.jca.core.connectionmanager.listener.TxConnectionListener$TransactionSynchronization.afterCompletion(TxConnectionListener.java:1155)
at org.jboss.jca.core.connectionmanager.transaction.TransactionSynchronizer.invokeAfter(TransactionSynchronizer.java:456)
at org.jboss.jca.core.connectionmanager.transaction.TransactionSynchronizer.afterCompletion(TransactionSynchronizer.java:392)
at org.jboss.as.txn.service.internal.tsr.JCAOrderedLastSynchronizationList.afterCompletion(JCAOrderedLastSynchronizationList.java:163)
at com.arjuna.ats.internal.jta.resources.arjunacore.SynchronizationImple.afterCompletion(SynchronizationImple.java:96)
at com.arjuna.ats.arjuna.coordinator.TwoPhaseCoordinator.afterCompletion(TwoPhaseCoordinator.java:545)
at com.arjuna.ats.arjuna.coordinator.TwoPhaseCoordinator.end(TwoPhaseCoordinator.java:101)
at com.arjuna.ats.arjuna.AtomicAction.commit(AtomicAction.java:162)
at com.arjuna.ats.internal.jta.transaction.arjunacore.TransactionImple.commitAndDisassociate(TransactionImple.java:1200)
at com.arjuna.ats.internal.jta.transaction.arjunacore.BaseTransaction.commit(BaseTransaction.java:126)
at com.arjuna.ats.jbossatx.BaseTransactionManagerDelegate.commit(BaseTransactionManagerDelegate.java:89)
at org.jboss.tm.usertx.client.ServerVMClientUserTransaction.commit(ServerVMClientUserTransaction.java:193)