3204396 - Resource not found for segment 'Attachment' when trying to download a file in My Inbox

When trying to download an attachment of a Purchase Order in My Inbox application, Resource not found for segment 'Attachment' error is raised. 

The name of the file starts with "H_".

• Task Gateway
• Gateway Business Workflow Enablement
• ABAP PLATFORM - Application Server ABAP
• SAP Gateway
• My Inbox
• The attachment filename starts with "H_"

SAP_GWFND, IW_PGW, /IWPGW/TGW, /IWWRK/WORKFLOW, IW_BEP, TASKPROCESSING, MyInbox, F0862, CL_MM_PUR_PO_WFL_ATTACH_BADI, WF_ATTACHMENT_PROVIDER BAdI, GOS Attachment, ME21N, Create Purchase Order — Advanced, TS00800531, WS00800238, WF_OBJECT_ATTACHMENT, MM_PUR_PO_WFL_ATTACHMENT, CL_MM_PUR_PO_WFL_ATTACH_BADI, IF_ATTACHMENT_PROVIDER_BADI~GET_ATTACHMENT_LIST, LT_ATTACHMENTS, CONCATENATE 'H_' ls_attachment-filename INTO ls_attach-filename, LS_ATTACH-FILENAME, CM_MGW_RT, /IWBEP/CX_MGW_BUSI_EXCEPTION, Resource not found for segment 'Attachment'
, KBA , MM-FIO-PUR-REL , Fiori UI for Purchasing Approval , OPU-BSE-WFM , Gateway Business Workflow Enablement , OPU-BSC-TGW , Task Gateway , Problem