I've found that occasionally when you kill a counterattack toon (think warrior and assassin newborns of light from LoL) with reflect damage, the game will hang up and leave your team staring at the enemy with nothing you can do to finish the fight. This causes you to either have to exit or close the game, in which case you lose your SoW, whatever rewards you may have received, and trooper points as well.

I believe this bug may be caused by the fact that reflected damage causes counterattackers to want to counterattack again, so when some die from reflected damage but leave a survivor or two, the game hangs because (and this is my theory) the game registers the dead toons as wanting to counterattack, but they are no longer alive to do so. Not sure if that's the exact cause, but I believe that making it so counterattackers can't retaliate to reflected damage would fix this bug, as well as the annoying instances where counterattackers endlessly retaliate to reflected damage until they either kill themselves or kill your toons.