Solution : https://service.sap.com/sap/support/notes/515012 (SAP Service marketplace login required)
Key words : 
system issues error message ff762, fi-ca contract accounts receivable, fi-ca summary records, fi-gl general ledger, condition type & tax code &, contract accounts receivable, terms crm billing, crm billing, billing documents, transaction fpg1
Related Notes : 
       
| 427299 | FF804 during transfer from Billing Engine to R/3 |