Solution : https://service.sap.com/sap/support/notes/120546 (SAP Service marketplace login required)
Key words : 
symptom material requirements planning generates, additional key words md01, periodic lot-sizing procedure 2, attached advance corrections, lot size > 1 3, lot size = 1, procurement element, availability date, = availability date, planned order
Related Notes : 
       
| 331976 | Lot size acc. to flex.period lgth->incor. dely date | 
| 205121 | MD01: Incorrect dates during date specification = 3 | 
| 198871 | MRP: Procurement proposal in planning time fence | 
| 164682 | MRP: Procurement proposal in planning time fence | 
| 122198 | Lot size acc.to fl.prd lngth:proc.proposal too late |