Hello,
Since you have already tried testing out the registry and group policy editors, I want to clarify exactly how you are trying to pin these items.
Are you trying to right click a specific sub category like the About page or Windows Security from the navigation sidebar or are you clicking somewhere else?
Microsoft fundamentally changed the way the Settings app behaves in the newer Windows 11 updates you mentioned, and they actually removed the native ability to just right click and pin deep sub menus to the Start menu in a lot of places.
Let me know exactly what steps you are taking to pin those specific settings so I can see if your install is actually glitched or if you are just running into normal intended design changes.