NavBar gone when sorting with Category buttons


I have a page where I display all content from a collection list, at the top there are category buttons to sort.
The sorting works well - however, I lose my NavBar on all of the sorting pages (but not on the standard “All” page).
Interestingly, I have three of these pages, and it happens only to two of them…
(Projects is fine, Principal Investigators and News are not)

Would appreciate a hint where to look!

Here is my site Read-Only: Webflow - Metaflammation