I have too this problem
I see on others questions the use of bypassUpdates = "true" and flushMode = "manual" in Hibernate/JPA, but this have problems too:
Use bypassUpdates = true isn't appropriate, because the fields that are in the reRender don't show updated (And this is important when using AJAX).
Using flushMode = manual also does not solve the problem.
The model is not persisted in dataBase, but if you click a button like "Cancel" (with immediate = true), the object is still to the state in memory modified by Ajax. If another page to display the object, it will be with wrong values.
Somebody has some tips?