What causes this issue?

The transfer activity profile for this transfer type and activity
indicates that you want to book the goods issue for the deliveries in
this transfer to take place in the background.

System Response

The job is run in the background. The variants in the transfer activity
profile control whether the background job is released.
When the background job is executed sucessfully a job number is entered
in the application log. When a backgorund job is not carried out
successfully a return value is entered in the application log.

Error message extract from SAP system. Copyright SAP SE.