Solution : https://service.sap.com/sap/support/notes/691415 (SAP Service marketplace login required)
Key words : 
external data transfer, internal order, strategy sequence, automatic generation, settlement rule, order type, distribution rules, terms orext, ksr1_orc reason, program error
Related Notes : 
       
| 967485 | Internal order: Automatic generation with BAPI | 
| 876278 | SR Internal order: No generation w/ collective transaction | 
| 503993 | Claim: Settlement rule not taken from strategy sequence | 
| 301256 |