Hello, Domicilium CR, Laurent
We checked your menus and it works fine for us http://prntscr.com/vobahk and http://prntscr.com/vobbep . I can provide you the video if it’s needed.
Anyway, you may provide us with WP Dashboard and FTP access to your site and we could try to upload the improved version of the theme with some changes of the mobile menu scripts to check if it helps you. I see that you both use the CDN, so install the Cloudflare plugin and log in to the account to allow us to clear the CDN cache after the update.
Regards