Additional features, settings, or issues not covered by specific Microsoft Teams categories
Hello! My name is Mustafa, and I am an Independent Advisor as well as a long-time Microsoft user. I'm sorry that you are experiencing this issue, and I am hopeful that I will be able to help you find a satisfactory solution.
If you want to make someone an owner or view who's an owner of an existing team:
1: To the right of the team name, select More options button > Manage team.
2: Select the dropdown next to Members and guests to see all team members. The Role column on the right tells you if someone is a team member or team owner. To make someone an owner, select the dropdown and then choose Owner.
You can also make someone a team owner while you're creating a team. When you're adding team members, choose whether each new person is going to be a team member or team owner by selecting Owner under the Member menu.
Please visit this link below to read the official Microsoft article and see screenshots of the steps mentioned above: https://support.microsoft.com/en-us/office/make...
For your other problem, when you go to select another user as an admin please have a look if everyone is duplicated there also. And see if both accounts are online at the same time. Also, can you check the browser version of teams to check if this is the case everywhere? or is it only in one place that this issue is occuring?
Please let me know if this doesn't work or if you need further assistance.
Warm Regards,
Mustafa