Solution : https://service.sap.com/sap/support/notes/441506 (SAP Service marketplace login required)
Key words : 
system determines incorrect basic dates, additional key words md01, lead time scheduling solution, basic finish date, basic date adjustment, -house production time, attached program corrections, lead time scheduling, material requirements planning, backward scheduling activated
Related Notes : 
       
| 640207 | MD03, MD43: Incorrect planned order dates | 
| 603487 | Matl reqmts planning: No switching to forward scheduling | 
| 534380 | No adjustment of order finish date after lead time schedulng | 
| 434693 | Correctn for Note 406650: Reduction for lead time scheduling | 
| 406650 | No reduction during lead time scheduling |