Scenario:
- I have a site that has content in 2 languages: FR (french) and NL (dutch).
- The 403 page points to a special page that I translated in both languages.
- I have the language Detection & Selection settings in place (they work everywhere) 'nl' in the url > serve dutch content ... etc etc

Problem:
- When an anonymous user tries to access a forbidden page like www.mywebsite.com/nl/admin the language is NOT detected and (in my case) the French version is displayed ...

Could it be that the 403 error page "redirect" is not language aware ?