AFAIK, it's recommended to use manual flushMode and SMPC for all your conversations.
Not sure if I completely understand your situation/use case. Is there a conversation that begins before this one begins? If yes, show the metadata (@Begin, etc.)
Also, remember that you can programmatically set the flushMode in your code using the EntityManager interface:
but the flush-mode remains MANUAL after the conversation has ended
you can prove your hypothesis by using the API above (getFlushMode() in this case) to output the flushMode after the conversation has ended...