Platform, device version and operating system
What you were expecting to happen, and what actually happened
Expected delve chest to upgrade every time after doing all fights in the hall of the guardians. Delve chest didn´t upgrade after every fight in the hall of Guardians - it stayed white altough I won every fight.
How often does this happen? When did it begin happening?
Today once (second of three fights).
Steps to make it happen again
I had several bugs during the second fights when one of the enemy troops was still shown at the right side although won. I SUPPOSE these fights may not count as win.