The enemy Ares killed himself using Sunder. However, the Sunder tile was still created, but didn’t tick.
It was during the required 3* Magneto node in The Hunt: Alaska event. My team was 3* Thor, 3* Magneto, and 3* Iron Man. Enemy team was Ares, 2* Daken, and Moonstone. Daken was dead and Moonstone was still alive.
I’ve noticed similar bugs from one of the Iso mutant goons: one of their powers does self-damage and creates countdowns. If the self-damage kills the goon, the countdowns sometimes stick around and don’t tick down.