I have a weird problem. my site has 2 languages EN(Default)/AR

the Language selector on site behaves normal for logged in users

while for guest user when they cahnge the language to arabic it's good but when guest user try to switch back to english it's not changing

for guest user the link for:

Arabic Language is domain . com / ar

English Language is domain . com

while for logged in users 

English language is domain . com / en (which redirects to domain . com with english language

edit: also add to cart and buy now buttons are not responding in arabic language for guest user

how to fix this for guest users

v18 enterprise