thank you for the details. Can you check what the documents were every time this error occurred? Maybe the user in Action center didn’t validate any fields, required fields could be missing or they added an exception to the document in action center.
The way it is designed, our documents go into the action center, but if someone removes one of the document from the unassigned list, then the robot is kinda lost because the robot is still “processing” that vanished document. In the end, the ACResults are null and then, these empty data cannot be used by the train extractors scope as they are…empty.