The menu you see is not the correct menu. If you go into the menu admin section, you see a menu. That menu has been set just the way it should be. However, when you actually run the website, a totally different menu is used that's incorrect. It doesn't matter how much you modify the menu, that incorrect menu always shows up and always remains the same.
I did find a clue, however. If you go into the template and do a preview, the right menu appears and looks just like it's supposed to. If you click on any of the menu options, you go to the right page, but the menu is now incorrect.
Update: I just updated to the latest version of Joomla, 4.3.2. It installed correctly but the menu is still wrong. However, I see that I have two files overridden. They both seem related to the template. I don't know how they got overridden as I know I didn't do it. I also don't know how to check it out or how to fix what I find, which I also don't know about.
Perhaps that's where the trouble lies. What do you think?