Declan Curran Could you include your detach, merge, detach use case you discovered that seemed to persist the changes?

It's worth mentioning here in case you missed it in chat, EntityManager#detach states (per javadoc) that any unflushed changes made to an entity at the time of detach will be ignored. This would imply that prior to detach, any changes you've made with merge should be flushed based on your test case you included.