@mattdjuk This could be something (clutching at straws a bit here)...
I was just looking in the cookies, I see these:
Screenshot 2022-05-26 113221.png
It has 2 express.sid cookies
1 is for forum.$$$$$$$.co.uk and the other is for .$$$$$$$.co.uk
@baris tr-TR is probably coming from their browser. NodeBB will try to use the browser default language if possible.