Custom 404 page working for entire site

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,
1

We have a custom 404 page (https://www.matpriser.nu/error404) that works.

But when users are browsing our dynamic pages, they don’t land on the custom 404 page, but the old wix one.

This is a working dynamic page:
https://www.matpriser.nu/matleveranskollen/11865

And here is one that does not work.
https://www.matpriser.nu/matleveranskollen/22122

How can we make sure our custom 404 page works for the entire site?

Thanks!

2

This question has been asked before, and as far as I remember no one here had an answer.
Maybe Wix Support will be able to help.