Solution : https://service.sap.com/sap/support/notes/876718 (SAP Service marketplace login required)
Key words : 
switch bc sets reason, solution sap_basis support package 06, sap_basis support package 12, sap_basis support package 06, table entry texts, parameter zcsa/installed_languages, lang1/guide directory, terms transaction sfw5, call transaction sfw5, dialog box informing
Related Notes : 
       
| 1000586 | How to analyze missing translations / missing texts | 
| 908007 | Special functions in Switch Framework / SFW5 | 
| 877008 | Composite SAP note about Switch BC Sets | 
| 856284 | SAP ERP Central Component 6.0: Inst./upgrad and architecture | 
| 830722 | Current note for language transports in Release 7.0 | 
| 337623 | Customizing after installation or upgrade |