Homepage issue with WPML

I’m trying to configure wp fastest cache with wpml while I have chosen in WPML to server different languages from subdomains
meaning
english: domain.com
Russian ru.domain.com

I noticed an issue only on the homepage of the website but not at other pages.

The website serves as the cached version of the homepage the language that had the first hit. So if I clear the whole cache and go to domain.com and then go to ru.domain.com I see the english version of the homepage at both. Respectively if I clear the cache and visit first the ru.domain.com and then domain.com I see the Russian version in both. HTTPS is enabled on both.

Any ideas?

Thanks