Solution : https://service.sap.com/sap/support/notes/1645427 (SAP Service marketplace login required)
Key words : 
end user form, user group field, user group mandatory, eup img settings, user group, eup settings, msmp settings, stage level, error message, terms ac 10
Related Notes : 
       
| 1640992 | Master Note for SAP Access Control 10.0 - Support Pack 7 |