After loading this page in cswiki, the edit section links are both "edit source" although the first one opens the visual editor.
I debugged the scripts a bit (debug=1&safemode=1): Before executing JavaScript, there is only a single "edit source". When that finally happens, JavaScript tries to add the missing one by cloning the original one. However, since the condition on line 703 is false (mw.config.get( 'wgVisualEditorConfig' ).tabMessages.editsource is null which needs to be fixed), it keeps the original text.