[Risolto] My translations on the site goes missing plus everytime I edit translations from the classic editor ...

Background of the issue:
I am trying to translate the pages through the editor, but every time I save and look back after a few days or some time, the translations go missing. I am experiencing this issue on my site: link nascosto.

Symptoms:
Translations on the site go missing, and every time I edit translations from the classic editor, it gives me a warning.

Questions:
Why do my translations go missing after saving?
What causes the warning when editing translations in the classic editor?