Have the same problem, Local Storage: i18nextLng - de, nothing in Session and Cookies. Cleaned the Storage, nothing happens. In Console I have the following errors:
DevTools failed to pa**e SourceMap: http://192.168.1.99/static/css/main.a049ccfe.css.map
DevTools failed to pa**e SourceMap: http://192.168.1.99/static/js/main.666b1be8.js.map