Thanks for contacting WPML forums support. I'll be glad to help you today.
1) Please let me know how this page is created and translated. Also, please let me know if you use custom CSS for this page in the default language.
2) Could you please share your Debug information with me?
You can read a detailed explanation about it here. (http://wpml.org/faq/provide-debug-information-faster-support)
The debug info will give me a lot of information about how your site is configured.
Yes, I think there is indeed a different CSS for English. But that is not my intention. Where can I disable this?
I create the page in dutch via the WP Bakery Plugin. Once the dutch page was finished, I see the icon to translate the page into English, using WPML.
But to be honest, these menu pages are created to be used in both languages. So ideally I would link to the same page for Dutch and English. There is no need to translate.