2660638 - My Inbox approve/reject error - RFC call was not successful because of system failure

• When processing a task from the My Inbox application, after pressing approve/reject the following errors show up in the front-end:
  
  Cannot process task. For more information, see the details. RFC call was not successful because of system failure 'Screen output without connection to user.'.
  
  
  AND
  
  
• In the error log (/n/IWFND/ERROR_LOG), the following errors are raised in the front-end system:
  /IWFND/CM_MGW050 - Changeset processing failed.
  /IWFND/CM_MGW004 - RFC call was not successful because of system failure 'Screen output without connection to user.'.
  
  AND
  
  
• In the error log, the following errors are raised in the back-end system:
  /IWBEP/CM_MGW_BOP_RT012 -  RFC call was not successful because of system failure.
  
  
• The runtime error dump DYNPRO_SEND_IN_BACKGROUND is raised in transaction ST22.

• SAP NetWeaver
• SAP Web Application Server for SAP S/4 HANA
• Gateway Business Workflow Enablement
• ABAP PLATFORM - Application Server ABAP
• SAP Gateway

WF_GDPR, SAP_GWFND, IW_PGW, /IWPGW/TGW, /IWWRK/WORKFLOW, SWF_WORKFLOW, Gateway, CALL SCREEN, BAdI, _DPC, _DPC_EXT, OData, IW_FND, ABAP programming error, ST22, /IWBEP/FM_MGW_HANDLE_REQUEST, DYNPRO_SEND_IN_BACKGROUND,  /IWFND/CM_MGW 050, /IWFND/CM_MGW 004, /IWBEP/CM_MGW_BOP_RT 012 , KBA , OPU-BSC-TGW , Task Gateway , OPU-GW-COR , Framework , OPU-BSE-WFM , Gateway Business Workflow Enablement , OPU-BSE-SDE , SAP Data Enablement , Problem