Let's go back a step. The issue only happens with WPML AI translation. On your demo, for some reason, we can't use WPML AI to translate Greek as we should, while in mine we can.
Please see the following video where I explain and demonstrate this: hidden link
This is the first thing to fix, because otherwise we won't be able to replicate the issue.
We could also schedule a meeting to see this together.
Okay, I found the issue with our sandbox site is that the version of WPML AI is not the same. I'm creating a new fresh install on our cloudways server where we will be able to use the latest version of WPML AI which should include Greek to English automatic translation. As soon as I have that set up, I'll set up WPML and use only the WPML AI translation service and try to reproduce this issue.