Hela being auto downed

Last few times I've used Hela she randomly gets downed. Each time has been at the end of my turn, with no active powers or passives on her teammates. Nothing in her powers list suggests she kills herself, and there is no notice on screen. The most recent time I was fighting against Hammer goons and only made a standard match with 5* Dr Strange. After the match finished, Hela went from full health to immediately downed. This has been consistent with her character.