Getting Error PO through API . ORA-00001: unique constraint (PO.PO_LINES_U2) violated in Package po.

Hello Expert,

Hope you guys can help me. we are customize concurrent PO Auto create from requisition using  API. after applied Patch 24601864 we are getting a weird error message when run The concurrent Auto create, it was working fine previously but now it is failing with the following error debug:

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ORA-00001: unique constraint (PO.PO_LINES_U2) violated in Package po.plsql.PO_LINES_DRAFT_PKG. Procedure merge_changes.10User-Defined Exception in Package po.plsql.PO_LINES_DRAFT_PVT. Procedure apply_changes.40 User-Defined Exception in Package po.plsql.PO_DRAFTS_PVT. Procedure apply_changes.10 User-Defined Exception in Package po.plsql.PO_DRAFTS_PVT. Procedure transfer_draft_to_txn.40 User-Defined Exception in Package po.plsql.PO_PDOI_POSTPROC_PVT. Procedure transfer_draft_to_txn.10 User-Defined Exception in Package po.plsql.PO_PDOI_POSTPROC_PVT. Procedure create_update_doc.60 User-Defined Exception in Package po.plsql.PO_PDOI_POSTPROC_PVT. Procedure process.80 User-Defined Exception in Package po.plsql.PO_PDOI_PVT. Procedure start_process.120 User-Defined Exception at location 020 in Package PO_INTERFACE_S Procedure create_documents