I went to the Arena earlier to Battle with one of my pets and, after each battle, the selection bubble was still colored in. This has happened a couple times in the past but during those instances it happened on occasion, not after every battle, and the Accept Challenge button was lit up. Now, however, the bubble was staying colored after each battle and I had to select another pet, then reselect the original pet I was battling, to fight it again. I tested this with another pet and got the same results. Whether I won or lost the bubble remained selected and the Accept Challenge remained inactive until I selected another pet.

I also noticed this happening. Looks like this selection problem only happens with manual battle, autobattle is working fine.

I'm bumping this back up since it's still happening and I never got an answer as to why.