At first, thank you for your fast response.
Right after my post i tried many things to get away from this described behavior. I also restarted my device a few times.
Now, right after your response, i checked again with a few invites, and from now on it is showing the right calendar... i'm confused.
I've seen described behavior yesterday and today... Uhm, as it now works as expected, there must be some magic in the air
Thank you anyway, if it happens again, i'll have a deeper look into it.