I have not heard of this issue before but here are some things you can try.
Make sure on the browsers you use that your default language is set to your preferred language. Try clearing your browser cache and restarting. Check whatismyipaddress.com to see what location is shown by your IP as some websites will change your language based on your IP location, however, you said you disabled the DPN feature so that should not be the issue. Try using a private browser and see if these websites still default to Spanish.
Hopefully one of these suggestions help.
