Solution : https://service.sap.com/sap/support/notes/190810 (SAP Service marketplace login required)
Key words :
system generates error message >3001 'contract account &1, additional key words, letter is_u_move_in_welcome_letter, exist - change, prerequisites solution
Related Notes :
| 187264 | Collective note f. IS-U/CCS 4.51 - add-on patch 006 |