Solution : https://service.sap.com/sap/support/notes/1340625 (SAP Service marketplace login required)
Key words : 
attached source code correction instructions, formula tab view, item number renumbered, item number, existing item, deleted item, press <enter>, system deletes, renumbered items, terms rmwb
Related Notes : 
       
| 1026328 | Deleting formula items |