Form on multilingual website doesn't work

Website is located at https://bouzywineandfood.nl.

Main language is Dutch (NL), secondary language is English (EN). When viewed in Dutch, the booking form (located at #reserveren) works fine.

However, in English the booking form doesn't work...

The form itself starts with {{ form:create in="reserveren" redirect="/#reserveren" }}.

I've tested changing the redirect to "/en#reserveren" but that still doesn't work. When trying to submit the form in English, I get redirected to a 404 and I'm told that the page doesn't exist.

What am I missing?

Thanks!