Trainers may experience an issue where the Gym battle abruptly ends and a red "Error" banner appears at the top of the screen. This issue most often occurs when you move out-of-range of the Gym during the battle. However, this issue may also occur if your internet connection is lost in the middle of the battle. We are investigating better ways of displaying this error message to users.
While this functionality is working as intended, we are investigating better methods for displaying this information.