I was playing on Novice level today for about 95 minutes. I had a Strong army consisting of my Sovereign, two sand golems and two other heroes. I fought a Weak group of 4 Darklings that were wandering the land. One of my heroes, Raza the Wild, killed them all with a Throw Coals ability (or something similarly named). When the reward screen popped up, All of my units were rewarded with strange amounts of experience, some extremely high like +1717986944 and also like -2147483648. They began to level up wildly. Shortly after the game crashed.