Birthday Calendar reappears

Hey everybody,

I am currently trying to set up the calendar and contact environment for my company and keep running in the most ridiculous issues.

Today on the menu: Birthday Calendar.

We want to use a central contact book so that not everybody has to manage their own contact book. I tried around with public folders which works in theory but I couldn't find a way to set up an automated birthday calendar for public folders. So I decided to use a shared mailbox for that which seems to be working fine.

Now I don't require the personal birthday calendar anymore and a quick google search showed where to deactivate it. "Outlook Online - Settings - Calendar - Deactivate Birthday Calendar".

Now, the problem is that the birthday calendar reactivates it self every single time. I doesn't matter if I have the outlook app open or closed at the time. This calendar won't go away. 

After multiple tries I now have 5 personal Birthday Calendars in my outlook app. Anyone has an idea on how to solve this?

Thanks in advance and best regards.