Solution : https://service.sap.com/sap/support/notes/503745 (SAP Service marketplace login required)
Key words :
implement source code corrections, duplicate request schedule lines, attached control report z_cnt_schedlin, request schedule lines, initial data transfer, category 'executable program', /sapapo/schedlin reason, transaction /sapapo/bop_worklist, /sapapo/bop_worklistbackorder processing, control report