Gym problem or glitch or hack idk

Okay so here is my problem. We are trying to take a gym and this one guy called kingarruda has his Pokémon in there well you get it down and when it reaches the lowest CP possible for it the gym battle messes up. You battle it until its health reaches zero then nothing happens. Even if the timer reaches zero nothing happens. You can only run from the battle and itll give you an error message. So now we cant take any gyms from it because we cant kick his out if people feed it.

Rellik0191 about Pokémon GO, v1.37.2