When importing several documents at once (through D&D for instance), the logs are filled with JCR stacktraces due to conflicting concurrent editing of the 'WfinProgress' system property by the VersioningMessageListenerMessage Driven Bean. Maybe this bean should use a dedicated serial queue instead of the default topic "topic/NXPMessages" in order to avoid conflicting concurrency.
JMS / MDB expert insight welcome.
Stacktrace attached in comments.