Xbox party error?

I recently got the error that I'm disconnected at least 20 times a day from the xbox party, although my nat type is medium. Before it always worked, but if 3 of my friends come to the party or are the host, it is always disconnected or an error. Is it my internet or theirs?

Hard to say. Could also be a problem on the part of Microsoft.

But I still tap your NAT setting. This should always be open. And not only with you, but also with your friends.