Sudden language change on the platform

Need help!
Sometimes the language on the platform suddenly change to another language and when we check the language is ENGLISH default in the dropdown option also but the blocks on sprite lab, app lab all start coming in another language. Half in English and half in another language.
Teachers are facing these issues when teaching child and then class stops. So please give a solution that how to correct this error if the language not changed but still shows another language?