EntityManager is put to event Scope for better memory usage and GC.
Class that tries to use the entitymanager is itself in conversation scope, and this specific behavior occurs after icefaces file upload.
Injected em is closed and throws IllegalStateException for every function used (as it should when it's closed).
I dug around the persistence namespace/package and found once place that could explain it.
line 225 to 229
As seen, entityManager is closed but since getEntityManager() function only creates new entitymanager when entityMAnager is null and does not check for entityManager being closed, the closed entitymanager gets passed around.
I added entityManager = null; after the entityManager.close(); line so that the getEntityManager() would correctly return new entitymanager after old one was closed and recompiled the latest sources.
It seemed to fix this issue, no more errors, em injected to the conversation scope class is not closed one anymore
There may be some other things related to this like
JBSEAM-2666 but I'm not entirely sure about it.