stop_fines not set even though checkin has occurred

Running the following query, I've discovered cases in our system where the checkin_time is set, but the stop_fines_time and stop_fines reason are never set. This leads to cases where an item is considered returned, but the circulation continues to accrue fines.

SELECT *
FROM action.circulation
WHERE checkin_time IS NOT NULL
AND stop_fines IS NULL
AND xact_finish IS NULL;

Looking back at the checkin_scan_time, this has been happening to us occasionally since 4/24/12 (our 2.2 days).

Current suspicion is that there's some sort of timeout occurring. I can see entries in our logs like:

Processing circ 8857564...
No request was received in 8 seconds, exiting stateful session

Then it dies when trying to update that circulation (I can see CHECKIN being listed as part of the command) with:

No active transaction -- required for UPDATE

So I guess it doesn't actually process out the changes to the circulation even though it does seem to be logging the checkin_time, workstation, etc. first.

I'll continue trying to gather more information.