This has been a big for a while (before today’s update). How to reproduce:
- Open friends menu
- Click on a friend’s name you have an async duel with
- Enter the game and take your turn
- Leave the game and go back to the menu
- Open the friend menu again
After step 5, the battle prompt will still be present for the person you clicked before, instead of there being no battle prompt.
I then have to click elsewhere on the screen to remove this old battle prompt, and then can choose a new one.