The DNS server configuration part needs to be removed from the CGI.
Changes have been pushed to my personal git repository: https://git.ipfire.org/?p=people/stevee/ipfire-2.x.git;a=commit;h=456f0b06f4691cd7e07b9e5ec5bb86d0117c3456
https://blog.ipfire.org/post/ipfire-2-25-core-update-141-release