I was on level 14 of the rare event, second screen when there was a blank spot where a monster should be. Eventually, it showed as a suspicious chest, though the graphic didn’t show for a while. The issue is that the progress was completely frozen, even though the timer was still going. I couldn’t move any tiles or use my heroes specials, though my touch was registering.
After almost 8 minutes of this, I had to flee, losing the chest and the WE. I took pics at 2 different times, just to show timer progression, though no game progression happened.
I completed that level but never got another chest back