Event Receiver Not Found

[Robin Sahasranam]

We are productive (in 4.0b) with early archiving for posting GL documents and
linking it to image. We have configured to use standard task TS7869 ImageAssign.
Everything works fine, except the users want to be able to reject processing. As
this is only possible in a WF template, I created a custom WF template which has
the single step task TS7869 and changed the configuration (SOA0) to start the
custom WF instead of the task TS7869.
 
The WF starts fine, but the Workitem remains in STARTED status even after the
document is posted. The task should  be terminated by event IMAGE ASSIGNED. The
event log shows the event was created but has status "No receiver entered". The
event linkage for the event is enabled and has the following settings:
Receiver FM: SWW_WI_COMP_EVENT_RECEIVE
Check FM:     ARCHIV_WORKFLOW_ASSIGN
 
I am unable to figure out why the terminating event linkage to the workitem is
failing for my custom WF, but works when the task is directly started. Could the
Check FM have logic to prevent the event linkage?
 
Also, is there a way to online debug the Check FM either when executing the
workitem or when creating the terminating event via SWUE? Providing all the
possible data through SE37 is difficult because of the complex container table.
 
Thank you for your assistance.
 
Robin Sahasranam.