I have uploaded two test cases for Hibernate 4 and 5.
The test works for Hibernate 4 and fails for Hibernate 5.
Upon further investigation it turns out that the hibernate 5 test can be made to work if the following parameter (hibernate.jdbc.batch_size) is removed from persistence.xml.
Given that the entities use Identity columns, which has an affect on statement flushing, the use of the hibernate option may be breaking the flushing in v5