The EntityManager is closed

My solution.

Before doing anything check:

if (!$this->entityManager->isOpen()) {
    $this->entityManager = $this->entityManager->create(
        $this->entityManager->getConnection(),
        $this->entityManager->getConfiguration()
    );
}

All entities will be saved. But it is handy for particular class or some cases. If you have some services with injected entitymanager, it still be closed.