"java.lang.IllegalStateException: EntityManagerFactory is closed" in JBoss EAP

Issue

Encountering an "EntityManagerFactory is closed" error when trying to work with container managed entity manager instances.

... java.lang.IllegalStateException: EntityManagerFactory is closed
        at org.hibernate.internal.SessionFactoryImpl.validateNotClosed(SessionFactoryImpl.java:531)
        at org.hibernate.internal.SessionFactoryImpl.getProperties(SessionFactoryImpl.java:525)
        at org.jboss.as.jpa.config.Configuration.skipMixedSynchronizationTypeCheck(Configuration.java:345)
        at org.jboss.as.jpa.container.TransactionScopedEntityManager.testForMixedSynchronizationTypes(TransactionScopedEntityManager.java:215)
        at org.jboss.as.jpa.container.TransactionScopedEntityManager.getOrCreateTransactionScopedEntityManager(TransactionScopedEntityManager.java:166)
        at org.jboss.as.jpa.container.TransactionScopedEntityManager.getEntityManager(TransactionScopedEntityManager.java:87)
        ...