Zero damage bug
 

I keep getting a bug where a spell is cast against my troops, it causes 0 damage but the entire unit is destroyed. I've read about this online so I think it is known about. Is there a way to fix it?

It's very annoying as it happens in almost every hero or item battle now and I don't want to lose a complete stack every time I fight a hero!

It didn't happen when I played as a skald or for the first part of my current soothsayer game. But now that I've got to the middle portion of the (soothsayer) game it happens all the time! From my online research it appears to only happen to soothsayers and later in the game, could it be linked to the 3rd level of the higher magic promotion (I only relatively recently unlocked it)?