Exception 'org.hibernate.HibernateException: Duplicate identifier in table' in JBoss EAP 7

Issue

Received an error in our JBoss logs concerning a duplicate identifier in table. Here is an excerpt of the error:

Caused by: org.hibernate.HibernateException: Duplicate identifier in table for: [com.xxxx.framework.model.notification.NotificationRecipient#27173]
        at org.hibernate.persister.entity.AbstractEntityPersister.check(AbstractEntityPersister.java:2548)
        at org.hibernate.persister.entity.AbstractEntityPersister.update(AbstractEntityPersister.java:3376)
        at org.hibernate.persister.entity.AbstractEntityPersister.updateOrInsert(AbstractEntityPersister.java:3250)
        at org.hibernate.persister.entity.AbstractEntityPersister.update(AbstractEntityPersister.java:3651)
        at org.hibernate.action.internal.EntityUpdateAction.execute(EntityUpdateAction.java:146)
        at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:604)
        at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:478)
        at org.hibernate.event.internal.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:356)
        at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:39)
        at org.hibernate.internal.SessionImpl.doFlush(SessionImpl.java:1472)
        ... 142 more