What you were expecting to happen, and what actually happened?
Attempt to set Team #1 as my defensive team, have team 1 be the defensive team.
What are the steps to make it happen again?
Set any other team as the defensive team. Exit, and reenter, see that team is the defending team. Try to set team #1 as the defensive team. Exit and return, and the previous team will still be the defenders, not team #1.
I have the same problem. Completely unable to set Team 1 as defence. My experience reproduces OP’s behaviour exactly. Playing on multiple Android devices, mainly Marshmallow on Nexus 7.