Advanced queuing - message state=expired

Hello

I use AQ and Forms to send scanner Information to forms.

DB-Version: 11.2.0.4.0

Forms: 11.1.2.2.0

I use event correlation to get the right message in my form:

Set_Event_Object_Property(v_EventID, EVENT_CORRELATION_ID, c.arb_platz);

Set_Event_Object_Property(v_EventID, EVENT_ENABLED, PROPERTY_TRUE);

It works since many weeks without any problem, but since 1 week I get sometimes not the requiered event in forms and the message get state=expired in the Queue. The problem exists only a short time of some minutes.

I testet with nearly hundred messages and it worked.

Is there any tracing or logging available in AQ?