Workflow is not triggered on Idoc error

Hi Gurus:

I'm not sure if this is the correct place to make this question. This is related to Workflow and Idocs.

There is a new request to trigger a workitem once a custom Idoc fails (status 51). This custom Idoc is processed by a custom Function Module (tx WE42).

I configured (tx. WE42 - Inbound Process Code) IDOCAPPL as Idoc Type as well as INPUTERROROCCURED as start event . Then, I linked (under tx. SWE2) IDOCAPPL-INPUTERROROCCURED to standard task TS20000051.

I created some Idocs with status 51, but the event wasn't triggered (it doesn't appear in the SWEL event trace). I compared my configuration with another config from a standard message type and both are the same (even both are using same Object Type and start event).

Do you know what could be happening? Does the custom FM could be the problem?

Thanks in advance,

Rodrigo,