hrvoje_hr Linguist doesn't make use of any foreign key.
You should have indexes for PRIMARY(id), INDEX(key), INDEX(locale) and UNIQUE(key,locale)
If the table is broken, you could create a database backup "data-only" for the table, disable the extension, select "uninstall" in the admin panel, then enable the extension, then re-import your "data-only" backup in the now-fixed table. Selecting "uninstall" and then re-enabling will rebuild the extension tables (and delete the data inside of those tables)
