I have a business site (www.go4people.nl) with multiple "business units" (Inspiratie & Advies, Onderwijs, MKB, etc). I have one custom-made template with a template style for each unit.
I do use one SEO top menu structure with system links to avoid duplicate content.
Below all business units there is a menu-item (specific for that unit) called "Nieuws" which is a category blog using a specific tag for that business unit. So all news-items have the category "News" and a tag for the specific unit.
The news module uses the same selection of a category and a tag, which works fine. Also the menu item shows only articles with tag and category. My problem is that when opening a specific news item from the module on the frontpage, it will allways open in the menu under "Inspiratie & Advies", even though the item has a tag for another unit.
If you want to check, go to https://go4people.nl/onderwijs and select a news-item in the upper module. It will bring you tou the I&A Frontpage, even though there is also a Category blog menu item with the tag Onderwijs under that part of the menu.
Am I missing something or is this by design?
Joomla does not handle routing well if a single category is assigned to multiple menu items.
The routing system looks for the menu item that the category is assigned to. Once it finds it, it does not look for another one.
This means that if you have a single category assigned to multiple menu items, the routing system (which is responsible for building module links too) will always link to only one of the menu items.
To fix this you will either need to use a separate category/subcategory for each menu item (aka business units) or use a tag to identify "News". Essentially, swap how you are using tags and categories.