2497131 - Error /SAPSLL/API_INBOUND 077 "Reference document is already being processed; cannot be created"

Symptom 1:

Multiple proforma invoices for same delivery are not transferred to GTS
When proforma billing document is split into two, one of the document is processed successfully but the second one fails
If single delivery is created for a sales order, but the proforma Invoice is split due to some reason, the transfer of invoice fails for one of the invoices with error message /SAPSLL/API_INBOUND 077 "Reference document XXXX is already being processed; cannot be created"

Symptom 2:

Invoices based on the same handling unit in the Outbound delivery are not transferred to GTS. Error Message "Creation not allowed; transaction already transferred to SAP GTS Message no. SR053" is raised.

• Global Trade Services (GTS)
• Global Trade Services / Logistics Services (SLL)
• SAP Global Trade Services
• GTS Plug_in
• SAP R/3
• SAP R/3 Enterprise 4.7
• SAP ERP Central Component
• SAP ERP
• SAP Enhancement package for SAP ERP
• SAP Enhancement package for SAP ERP, version for SAP HANA

/SAPSLL/API_INBOUND077, Customs, References, /SAPSLL/API_6800_CSD_SYNCH, /SAPSLL/API_6800_CSD, /SAPSLL/CORREF, /SAPSLL/CORREF_ENQ_S, enqueue, billing, splitting, LUW, queue, log, SLG1, /SAPSLL/EXPORT_TLOG, ERP, ECC, sales orders, shipping, shipments, feeder, system, cancel, /SAPSLL/ECORREF, CUHD, CORREF, SAPSLL/CUHD_REGISTRATION_CHCK , KBA , SLL-LEG-CUS-DOC , Customs: Document Processing , SLL-LEG-PI-R3 , PI: R/3 , Problem