I was looking into creating a Timeline for our teams progess and when grouped by Team i have all issues grouped in teams as requested, but I also see all the issues in the "Unassigned" Team
the first screenshot shows the Dev team:

Below the Dev team there is the "Unassigned" section

Eventough, the stories are assigned to dev and team and sprint, they still appear in the unassgned catory & the dev team, i don't know what else to assign them too.