After hours of investigation into a similar issue we're seeing, we're pretty sure we're also seeing this same issue with the following versions:

• Spring 3.0.5
• Hibernate EntityManager 3.4.0
• Weblogic 10.3.5/10.3.6
• Oracle 12.1.0.2
  Adding the property to our persistence.xml to disable envers doesn't seem to have any effect, but forcing a manual flush does allow an error like ConstraintViolationException to surface, whereas without the manual flush it gets hidden when the flush is triggered before the commit, we only see the UnexpectedRollbackException and a nested RollbackException.

Given that manually forcing a flush seems heavy handed and not really the right thing to do, what's the way forward with this issue? We're seeing this issue with a production system, so options for upgrades to later versions of anything are limited. Is there or will there be a patch for the issue?