Everytime the team-leader/squad-leader die and respawn he loose his status as being the leader. This status is passed on to the next in command.
If the player being the new commander dies and respawn then the teamleader often get his title as teamleader back, and regain control of his team. ( but not always ).
I/we also belive the above often make the modules like artellery module stop working since the arma3 do not understand what happen when the team leader function are given to someone els while the teamleader is "respawning".
I experienced this bug alot of times while playing in my clan.