Solution : https://service.sap.com/sap/support/notes/1024707 (SAP Service marketplace login required)
Key words :
FP-EVENT_1108, FP-REQ, FPE1, FPE2, RE-FX, KONTT, KONTL
SAP Note 1024707 - FMCA_EVENT_6500: Event 1108 not called
Component : Public Sector Contract Accounting - Posting / Documents