This happens occasionally on iOS, either iPhone 10 or iPad Pro -
The fight essentially finishes, either with a loss or a win, but the "Victory" prompt doesn't show up and instead the winner can put more cards on the arena, and both players typically make fart noises while waiting for the backend to decide the fight is over. It only happened to me when the fight went into overtime.

https://imgur.com/a/vvTVvPu
https://imgur.com/a/eDh9vab