There should be a problem then as i am testing it also on on two different iphones and it's behaving the same as in my video which is not the way I am expecting this to behave.
Please click on the "produits" menu link to go to this page. And then once you are seeing the "produits" page then click on the submenus items (Local seeds, good food, cool kids...) then it will react the same way as mentionned on my video.
Please find here anther video taken of my iphone : https://www.dropbox.com/s/ybok8lnb7hbf8va/IMG_0124.mp4?dl=0
I cannot believe that this is an exception on my side as I cleared cache on my browsers, at the server level too...
Thank you for testing again and give me a feedback as soon as possible.