Solution : https://service.sap.com/sap/support/notes/166167 (SAP Service marketplace login required)
Key words : 
additional key words interest calculation method, interest calculation method act/actp, accrued interest calculation, attached advance corrections, excessively long coupon, excessively long, calculating 1 day, program error, 1 day longer, calculated
Related Notes : 
       
| 312475 | Incorrct accrued interest calculation for act/actP | 
| 167080 | Incorrct accrued interest calculatn for long coupon | 
| 109587 | Interest calculation method act/act |