Solution : https://service.sap.com/sap/support/notes/163842 (SAP Service marketplace login required)
Key words : 
additional key words, low item numbers, engineering change management, item counter overflows, item counter, change option, physical limit, multiple assignment, deleting characteristics, characteristics disappear
Related Notes : 
       
| 195150 | |
| 181625 | |
| 173023 | |
| 166530 | @3Z@ Config. objects delete classification data |