Outlook events API returning no events

Question

I have two accounts, both of which are on different company Office365 subscriptions, when I go to get the events for the API user that works I get this value in the @odata.context response field:

https://graph.microsoft.com/v1.0/$metadata#users('11411b43-4305-4f16-a24f-576077f61bdd')/calendar/calendarView

However, when I go to get the events for the user that does not I get this:

https://graph.microsoft.com/v1.0/$metadata#users('outlook_641A3F439DDB71BC%40outlook.com')/calendar/calendarView

This is incredibly rare but does happen, it is almost like a temporary outlook user has been created just for my API.

This user can even act the same as the real user but I cannot see the events of the real user nor write to their calendar, instead to some empty calendar they cannot see. I can see their calendar list but not events.

It is almost like some kind of approval user or something.

Does anyone know what does this? And if so how to fix it?