Ok @texnixe, if I force SSL and deactivate language detection, the error doesn’t appear, excepting when I send the contact form.
The strange thing is that is not necessary to do it with langkit on the same server. It seems as something is not fine in my code but I don’t find it.
Moreover, I can’t access the panel, both with my site and langkit, it redirects me to https://panel/login. It’s the first time I see this problem.