There are numerous redirects and old permalinks to articles that have been rewritten over the years with harmless fragments still part of the link that no longer point anywhere. These degrade gracefully and land readers at the top the article with either the information righ there, or easily fond via the table of contents (e.g. if the section got renamed), or simply not bothered if the link wasn't intended as a permalink in the first place (surprisingly common).
Example:
* https://office.wikimedia.org/wiki/Quarters#Bla (direct)
* https://office.wikimedia.org/wiki/Q3 (redirect)
* https://wikitech.wikimedia.org/wiki/Banana#X (non-existent article, possibly its own issue?)
I was not able to reproduce the issue at:
* https://wikitech.wikimedia.org/wiki/MediaWiki_at_WMF#Appservers
* https://nl.wikipedia.org/wiki/Lijst_van_Stolpersteine_in_Nijmegen#Foo
It does also show on these pages on the same wikis, but that's expected as these are talk pages:
* https://nl.wikipedia.org/wiki/Wikipedia:Te_beoordelen_categorie%C3%ABn#Foo (discussion in non-talk namespace)
* https://nl.wikipedia.org/wiki/Overleg:Lijst_van_Stolpersteine_in_Nijmegen#Foo (article talk)