Users report that Monitoring plugin is not using the main language set in Admin Console and instead looks into system's locale and tries to use an according language file. E.g. if a user has set English as his main Admin Console language, but has Russian as his region in OS, then Monitoring plugin shows Russian translation for menus. This is not consistent with how other plugins operate.
This is especially problematic for Russian users as Russian translation file is bad and shows garbled text, but one can't work around it by using English as a main language, as it still shows garbled Russian menus as Russian region is set in OS.