Reported about this a long time ago, but nothing happened as a result, so I guess it's a good idea to track it.
For some reason on every wiki that is using FlaggedRevs [[Special:NewPages]] page is unaccessible (returns some HTTP error):
https://isv.miraheze.org/wiki/Special:NewPages
https://tutor.miraheze.org/wiki/Istimewa:Halaman_baru
https://pornganizer.miraheze.org/wiki/Special:NewPages
etc.
Probably some bug in the extension, but I don't recall it being tracked down when I reported it at #miraheze.