IDOC is not processed in WF

[Christian Behla (QDD)]

Hi workflowers,
 
my 4.6B workflow ist triggered by IDOCORDERS / INPUTERROROCCURED.
After the first step (correcting data in background) i use method INPUTBACKGROUND.
This returnes without errormessage but the IDOC is not processed and IDOC-Status is 51: "Idoc ** could not be opened".
When i start the method in the workflow with a delay of 10 min, I still have the problem.
 
When i test the method in SWUD it works.
In EDI I have no problem processing the IDOC.
 
My idea is that somehow the IDOC is blocked.
 
Thank you in advance for any input you can provide.
 
Christian Behla