Device: Xperia Z5 Compact

OS: android

WTR (more "how it happened"):

Step 1: Go to CB battle easy, with 4 mil left on the boss

Step 2: fight it until you've reach the treshold for max reward (I overdid it a bit)

Step 3: leave the battle and see that the boss died in the mean time

Step 4: get no chest

Description:

Below is the damage done:

Regards