This isnt the first time. Its been happening since like 2 updates ago but there is a glitch when Tamsin uses their hero power. It eats 2 minions. And something like that can sway the game
It happens when you play a round with Tamsin as the second board, but your teammate is able to solo kill both ennemy warbands.
Your hero power has not been consummed and you stack it if you use it again
this is only a issue in duos