[Risolto] Translation issue after WP update to last version

Background of the issue:
I am trying to ensure that all translations on my website are displayed correctly in French or German. Since the last WordPress update, some pages are showing translations in English instead. The issue can be seen on this page: link nascosto

Symptoms:
Translations are appearing in English instead of French or German on some pages after the last WordPress update.

Questions:
Why are translations showing in English instead of French or German after the WordPress update?
How can I fix the translation issue on the affected pages?