When you finish a session. Don't stop the auto import.
Let the auto import running for another 15 minutes.
Or manually move the handhistory files to your archive folder.
So the next session you play, the handhistory folder is completely empty.
Then HoldemManager should register it as a new session.
You can also change the session duration time.
Edit postgresql.conf: default time is 30 minutes. So if you take a 25 minute break. The next session will be included in your first session.
HTML Code:
SessionTimeoutDuration">30</setting
Try changing it to a lower value like "10".