Solution : https://service.sap.com/sap/support/notes/1124458 (SAP Service marketplace login required)
Key words : 
solution source code correction, joint venture assignments, fi posting made, joint venture assignment, append structure t8jafvc, joint venture data, activity-assigned network, network activity derives, network activity, network header
Related Notes : 
       
| 1153990 | |
| 481002 | Upgrade to SAP R/3 Enterprise/SAP ECC with CA-JVA | 
| 316815 | CA-JVA: Upgr. R/3 Enterprise / ECC- data transfer AFVC->AFVU |