[Résolu] sticky header works with main language [EN] but not with translated languages [CN] [DE] etc

Background of the issue:
I am trying to create a sticky header. The sticky header works with the main language [EN] but not with translated languages [CN] [DE] etc. Link to a page where the issue can be seen: lien caché

Symptoms:
The header is not sticky in the translated languages.

Questions:
Why is the sticky header not working in the translated languages?
How can I make the sticky header work in the translated languages?